Alongside the smartwatch, gym towel, and set of earbuds, the shaker bottle has become a fitness gear staple to round out any dedicated gym-goer’s starter pack. This part-kitchen-appliance part-workout-accessory totes contents that can aid on-the-go nutritional needs, improve post-workout recovery, and facilitate muscle-building gains.

“Shaker bottles are a convenient way to shake up anything liquid you might need to mix: greens supplements to drink, powdered medicine, or even homemade salad dressing,” Ellyn Ferriter, MPH, CPT, certified personal trainer and group fitness instructor at Life Time, says. “They make it incredibly convenient to meet your daily protein needs when solid foods alone aren’t enough.”

Tested & Approved

The GNC Pro Performance JAXX Shaker Cup is our top pick because it’s durable, effective, and budget-friendly. We also like the Blendjet 2 for its powerhouse blending capabilities and versatility.

Whether you’re looking to gain muscle mass or need added protein in your diet, there are a lot of different uses for protein powder, says Allison Knott, MS, RDN, CSSD, a board-certified specialist in sports nutrition who guided our testers on test day. 

To find the best shaker bottles on the market, we shook things up in The Verywell Testing Lab. Under the guidance of Knott, six of our expert testers evaluated 29 top-rated shaker bottles. They assessed each bottle for design, effectiveness, and ease of cleaning—rating each bottle on a scale from 1 (would not recommend) to 5 (highly recommend) in each key category. 

Based on our test, here are the best shaker bottles on the market.

GNC’s Pro Performance shaker cup is lightweight, easy to carry, and (most importantly) provides a smooth serving of protein. At such a great value, it would have been our best budget pick. But it performed exceptionally well compared to the rest of the products we tested, making it an obvious choice for our best overall spot. Our tester loved the bottle’s design and appreciated the top handle for easy, on-the-go use. 

Best Overall

GNC Pro Performance Jaxx Blender Bottle

  • Handle for easy portability

  • Competitive price

  • Fits into cup holders

  • Not insulated

The shaker comes with a Jaxx mixer that was quick to eliminate any clumps—earning the bottle a 4.8 out of 5 for effectiveness. After enjoying a clump-free protein shake, our tester cleaned out the bottle with ease. No residue or odor was left behind, according to our tester.

Testing Notes: “This product does everything it is intended to do. It is simple and affordable, and sometimes that’s all you need.”

What Experts Say: “If you have any allergies, sensitivities, or other contraindications with medications you’re taking, you should be cautious when choosing a protein powder. Consulting with your healthcare provider is always a good idea”

GNC’s Pro Performance shaker cup does everything it’s intended to do. It’s efficient, effective, and easy to maintain—all you can ask for in a quality shaker bottle. 

Price at time of publication: $10

Key Specs:Capacity: 28 ounces | Material: BPA-free plastic | Blending Mechanism: Jaxx mixer | Insulated: No | Dishwasher Safe: No

This vessel does far more than a classic shaker cup—it can blend things like ice, frozen fruit, leafy greens, and more. It’s a versatile product that’s well worth the investment, according to our tester. With compact portability, a long-lasting charge, and a 6-point stainless steel blade, the Blendjet 2 is a portable blender machine. 

Best Investment

BlendJet 2 Portable Blender

  • Comes in a variety of fun colors
  • Extremely versatile
  • Handle for easy portability

For the purposes of this test, our tester used the device to make a protein shake. And after adding two scoops of protein powder to the well-labeled cup, she pressed the button and, within one minute, had a clump-free, frothy, and smooth protein shake. 

Testing Notes: “It’s a sleek and modern take on protein blending. Very effective for those who are busy and need to mix quickly.”

The Blendjet earned a perfect score of 5 out of 5 for effectiveness and ease of cleaning. It’s simple to maintain and clean, only requiring a quick wash with a simple soap and water solution after use. 

Price at time of publication: $50

Key Specs:Capacity: 16 ounces | Material: BPA-free plastic | Blending Mechanism: 6-point stainless steel blade | Insulated: No | Dishwasher Safe: No

The Contigo Shake & Go shaker bottle has a convenient carry loop, a leak-proof design, and a large capacity. It fits into a standard car cup holder, so it’s perfect for when you’re rushing to a gym session or taking your breakfast on the go.

Best On-the-Go

Contigo Shake and Go Fit Shaker Bottle

  • Unique shaker ball is easy to clean
  • Competitive price
  • Snap-shut design

The dense shaker ball makes for easy and effective mixing, earning it a perfect score of 5 out of 5 for effectiveness. After shaking for just 30 seconds, our tester enjoyed a smooth and satisfying protein shake. 

Testing Notes: “It sports these nice vertical bars on the outside of the container that make it easy to grip the bottle, a nice carry loop on the lid, and BPA-free plastic.”

Cleaning was simple and seamless, according to our tester. The unique textured design of the shaker ball was easier to clean than its spiraled stainless-steel counterparts. While this shaker cup is a great choice for on-the-go use, we recommend that its contents be consumed quickly because it isn’t insulated.

Price at time of publication: $12

Key Specs:Capacity: 28 ounces | Material: BPA-free plastic | Blending Mechanism: Weighted shaker ball | Insulated: No | Dishwasher Safe: Yes, top rack only

With a unique helix-shaped design, Helimix’s 2.0 Vortex shaker cup doesn’t require a mixing ball or blender blades to effectively make a smooth protein shake. And with one less item to wash, this shaker cup is hassle-free and earned a perfect score of 5 out of 5 for ease of cleaning.

Easiest to Clean

Helimix Vortex Blender Shaker Bottle

  • Doesn’t require added shaking accessories
  • Easy-to-read measurements
  • Snap-shut design

The product performs just as well as its competitors without requiring any added blending mechanism. And our tester said that the protein powder and water were so well mixed that the protein shake was left looking smooth and frothy. But the bottle isn’t insulated, so it’s important to drink your concoction quickly to avoid any spoilage.

Testing Notes: “The product feels nice and premium, and I can’t recommend it enough. The fact that it can mix well without a shaker ball is game-changing.”

The spout is wide and snaps shut, making it completely leak-proof and easy to drink on the go. Our tester appreciated these features that make it an easy pick for daily use.

Price at time of publication: $25

Key Specs:Capacity: 28 ounces | Material: BPA-free plastic | Blending Mechanism: Helix walls of cup | Insulated: No | Dishwasher Safe: Yes, top rack only

VOLTRX’s Premium Electric Protein Shaker Bottle uses BPA-free plastic blades and a strong motor to perfectly blend your pre- or post-workout drink. After two minutes of hands-free blending, our tester enjoyed a smooth and clump-free protein shake. 

Best Electric

VOLTRX Premium Electric Protein Shaker Bottle

  • Easy to clean

  • Doesn’t require manual mixing

  • Long-lasting charge

  • Measurements are difficult to read

The bottle has a sleek and silent design, which is great for mixing up a post-workout snack at the gym without distracting those around you. To clean, you simply fill the bottle up with water, add some soap, run the blender, and rinse—the bottle simply cleans itself, which our tester loved. 

Testing Notes: “After two minutes, it was ready to go and nicely mixed. I actually enjoyed the drink.”

Because of the bottle’s unique shape, the measurement markings found on its side are difficult to read, our tester said. This slight inconvenience is what earned the VOLTRX shaker cup a 4.3 out of 5 stars for design.

Price at time of publication: $55

Key Specs:Capacity: 24 ounces | Material: BPA-free plastic | Blending Mechanism: BPA-free plastic blades | Insulated: No | Dishwasher Safe: No

Featuring double-walled insulation, this Matrix shaker bottle will keep your cold or hot drinks temperature controlled. It’s leak-proof and has a convenient handle for easy portability. We like that the bottle has a sleek and versatile design, perfect to sport at the gym or in the office. 

Best Insulated

Matrix Insulated Shaker Bottle

  • Comes in a variety of fun colors

  • Handle for easy portability

  • Large capacity

  • Doesn’t have measurement markings

The shaker cup seamlessly combines liquid and powder through a removable, honeycomb-patterned lid agitator. After shaking the vessel thoroughly, our tester enjoyed a smooth, clump-free protein shake. 

Testing Notes: “I would recommend this product to anyone who’s looking for a bottle that can double as a workout bottle and as a bottle you can take to work and put any beverage in.”

The bottles’ stainless steel material made cleaning a breeze, according to our tester, who gave it a near-perfect score of 4.9 out of 5 for ease of cleaning. We recommend this product for on-the-go users with busy lifestyles looking to keep their shakes, smoothies, and drinks temperature-controlled.

Price at time of publication: $20

Key Specs:Capacity: 30 ounces | Material: Stainless steel | Blending Mechanism: Lid agitator | Insulated: Yes | Dishwasher Safe: Yes

The California Performance Co. Stainless Steel Shaker bottle is lightweight, has clear measurement markings, and has a snap-shut spout for leak-proof security. Our tester liked the bottle’s design but wished it had a handle for easier portability. 

Best Stainless Steel

California Performance Co. Stainless Steel Shaker

  • Competitive price

  • Comes in a variety of fun colors

  • Lightweight design

  • No handle

After just 15 seconds of shaking, the bottle and metal shaker ball produced a frothy and smooth protein shake—earning the bottle a perfect score of 5 out of 5 for effectiveness. Our tester also found the bottle to be super user-friendly. 

Testing Notes: “The shake came out frothy and looked really appealing. It has a shaker ball inside the bottle that worked really well.”

The stainless steel shaker bottle was super easy to clean after one use. But the lid has a built-in agitator that our tester suspects might accumulate buildup following long-term use.

Price at time of publication: $16

Key Specs:Capacity: 25 ounces | Material: Stainless steel | Blending Mechanism: Blender ball | Insulated: Yes | Dishwasher safe: Not listed

With two inner compartments and two snap-shut mouth spouts, the Hydra Cup Dual Threat is the best 2-in-1 shaker bottle we tested. We recommend it for those looking to store both pre- and post-workout drinks for on-the-go sipping. Our tester appreciated the latch-on lid and carry loop for worry-free portability. 

Best 2-in-1

Hydra Cup Dual Threat Shaker Bottle

  • Snap-shut design

  • Large capacity

  • Comes in a 3-pack

  • Not insulated

  • No handle

The bottle features two agitator lids that work independently to combine the powder and liquid in each compartment without any cross-mixing. Our tester found this design to be thorough and effective—giving the bottle a perfect score of 5 out of 5 for effectiveness. 

Testing Notes: “I would recommend this to anyone who needs a pre- and post-workout beverage but wants to consolidate both beverages into one bottle.”

Because of the unique dual-compartment system, the bottle was somewhat difficult to clean. The smaller, 12-ounce side requires a long scrub brush, as our tester noted, after a failed attempt to reach in with his hand to manually clean this side of the bottle.

Key Specs:Capacity: 22-ounce compartment and 12-ounce compartment | Material: BPA-free plastic | Blending Mechanism: Lid agitator | Insulated: No | Dishwasher Safe: Yes

If you’re looking for a no-frills bottle that will provide a smooth and satisfying pre- or post-workout shake, the BlenderBottle Radian Shaker Bottle is for you. Our tester enjoyed the design of this bottle—highlighting the durable aluminum finish, secure grip, and wide mouth spout for easy sipping. 

Best Classic

BlenderBottle Radian Insulated Shaker Bottle

  • Handle for easy portability

  • Easy-to-read measurements

  • Double-wall vacuum insulation

  • Lid may leak

The wire blending ball is standard but gets the job done, earning a 4 out of 5 for effectiveness. After 30 seconds of shaking, the liquid and protein powder were well-combined. But the bottle and ball were quite noisy during mixing—a fine trade-off for the bottle’s high-quality durability, according to our tester. 

Testing Notes: “This is a durable shaker bottle that’ll last you quite a long time.”

Simplicity was apparent across the board with this product, as a soap and water solution cleared out any residue with ease. We appreciate that the bottle is effortless to clean—an important feature in any shaker bottle.

Key Specs:Capacity: 26 ounces | Material: Stainless steel | Blending Mechanism: Wire blender ball | Insulated: Yes | Dishwasher Safe: No

A foldable carry loop, twist cap, and sport grip provide added security and allow you to sport this bottle worry-free all day. Our tester appreciated these reliable features, as well as the bottle’s unique shape that made it even easier to hold. 

Best Leakproof

BlenderBottle SportMixer Tritan Grip Shaker Bottle

  • Competitive price
  • Comes in a variety of fun colors
  • Rubber grip for secure carrying

The included wire blender ball was effective at mixing the powder and liquid concoction, leaving a clump-free protein shake ready to enjoy. Our tester loved the rubber sport grip that rounds the bottle, which he found helpful for sipping during sweaty workout sessions. 

Testing Notes: “Not only does it do what it’s supposed to do, but the rubber grip and easy-to-tighten opening are an added convenience.”

Our tester gave BlenderBottle’s SportMixer Shaker Bottle a perfect score of 5 out of 5 for ease of cleaning because he didn’t find any hard-to-reach crevices that required additional cleaning tools. A simple soap and water solution and a quick shake did the trick, he said.

Price at time of publication: $15

Key Specs:Capacity: 28 ounces | Material: BPA-free plastic | Blending Mechanism: Wire blender ball | Insulated: No | Dishwasher Safe: Yes

PROMiXX’s Pro Shaker Rechargeable Bottle comes with a small compartment to store protein. This feature is perfect if you’re looking to bring pre- or post-workout powder on a walk or to the gym. Our tester appreciated this feature and the product’s excellent overall design. 

Best with Protein Storage

PROMiXX Pro Shaker Rechargeable Bottle

  • Long-lasting charge
  • Doesn’t require manual mixing
  • Snap-shut design

In terms of the blending mechanism, this bottle uses BPA-free plastic blades to mix together liquid and powder into a smooth and frothy drink. Our tester said the product was easy and convenient to use. 

Testing Notes: “This has a built-in container for extra protein powder, in case you want to mix a shake on the go, which is pretty awesome.”

What’s more, the device essentially cleans itself—earning a perfect score of 5 out of 5 for ease of cleaning. All you have to do is add a drop of soap and some water, push the machine’s blending button, and rinse. Our tester appreciated the effortless maintenance of this PROMIXX bottle.

Price at time of publication: $40

Key Specs:Capacity: 20 ounces | Material: BPA-free plastic | Blending Mechanism: BPA-free plastic blades | Insulated: No | Dishwasher Safe: No

We Also Tested

  • Blackube Electric Protein Shaker Bottle: Our tester appreciated that this shaker bottle is easy to grip, user-friendly, and super effective at mixing together a clump-free protein shake. But ultimately, this product did not impress us as much as the other shakers that made our list.
  • Ladder Sport Insulated Shaker Bottle: This bottle is sleek, simple, and provides a smooth protein shake. But it doesn’t have measurement markings on the bottle—a major inconvenience, according to our tester.
  • Nike Unisex - TR Hypercharge Shaker Bottle: After just 30 seconds of shaking, this Nike shaker bottle produced a smooth and frothy protein shake. But we found the design to be rather basic, with higher-quality options available.

How We Tested the Shaker Bottles

To find the best shaker bottles on the market, six of our expert testers spent hours in The Verywell Testing Lab evaluating 29 top-rated products. A good shaker bottle should have a leak-proof design, eliminate clumps, and be easy to clean—our testers assessed each bottle across these three criteria and more. 

How We Rated the Best Shaker Bottles

  • 4.8 to 5 stars: These are the best shaker bottles we tested. We recommend them without reservation.4.5 to 4.7 stars: These shaker bottles are excellent—they might have minor flaws, but we still recommend them.4.0 to 4.5 stars: We think these are great shaker bottles, but others are better.3.5 to 3.9 stars: These shaker bottles are just average.3.4 and below: We don’t recommend shaker bottles with this rating; you won’t find any on our list.

With guidance from Knott, a board-certified specialist in sports nutrition, our six testers got to shaking in the lab. 

Using a Vital Proteins Protein Powder, testers were instructed to fill each shaker bottle with the correct amount of water for the perfect powder-to-liquid ratio. Then, using the included measuring spoon, testers added a scoop of protein powder to each bottle. After sealing the shaker bottle securely, they shook vigorously for about 30 seconds, or as recommended by the manufacturer.  

Next, each tester was instructed to sip their protein shake and pay special attention to flavor and texture: How did it taste? Was the shake clumpy or smooth? How well did the powder dissolve? 

Afterward, testers poured out the remaining liquid and cleaned the shaker bottle according to the manufacturer’s instructions. 

Throughout this test, our testers took special note of several things: If the bottle provided clear measurements and an added mixing mechanism, if it was easy to carry and seal, how quickly and well the powder dissolved, the texture and consistency of the shake, and if the bottle was easy to clean and maintain. 

Testers then rated each bottle on a scale from 1 (would not recommend) to 5 (highly recommend) for design, effectiveness, and ease of cleaning.

What to Look For in a Shaker Bottle

Size

First things first, consider what size shaker you want. The capacity you need in a bottle depends on how much pre- or post-workout liquid protein, electrolyte drink, or smoothie you generally require for your fitness goals or nutritional needs.

Brands on the market offer anywhere from 16- to 24-ounce bottles as well as larger versions in whopping 45-ounce volumes. Whatever you spring for, ensure it’s easy to grip and shake to avoid messes when you’re in a pinch. The smallest bottle on our list is the Blendjet 2 at 16 ounces, while our largest, Matrix’s Insulated Shaker Bottle, has a 30-ounce capacity. 

Material

Avoid stinky and short-lived vessels with a bottle made of non-toxic, quality materials. Choose a brand that uses BPA-free plastic, metal, or glass with components that are odor-resistant and ideally dishwasher-safe for day-to-day use. “If you want your drinks to be kept cold for a while, stainless steel is the way to go, but plastic bottles are lighter for packing,” Ferriter says.

Metal or glass are generally easier to clean than plastic, especially at times when your trusty shaker might sit all day in your bag or car before making it home.

Leak-Proof Design

No one wants a mess on their hands, so selecting something with a well-designed, secure lid construction is vital for shaker function and transportation. Since your protein shake might be sitting or jostling in your bag between stops, aim for a brand with a leak-proof guarantee of its seals, cap, and lid. BlenderBottle’s SportMixer Shaker Bottle is the best leak-proof bottle we tested. 

Positive ratings from users who put the product to the test, as well as a manufacturer-backed warranty, are things to look for when evaluating the leakproof-ness of a shaker bottle. 

Blending Mechanism

Your bottle’s internal mixing system should be effective enough to blend any powder into your liquid base. Options ranging from metal or plastic whisk-like balls to solid silicone or plastic mechanisms will all efficiently break up clumps. And bottles with screens, like Matrix’s Insulated Shaker Bottle, agitate ingredients just as well while shaking.

Ferriter favors wire spheres for her shakers. “They can mix all the way through your drink. That said, the screw top agitator lids have their purpose, too," she says. While stainless steel balls are typically an odor-free and easy-to-clean part, BPA-free plastic and silicone components tend to be less noisy, so this mostly comes down to personal preference.

Additional Storage and Features

If a multi-functional design is helpful to your routine, consider a shaker bottle with extra storage compartments for items like vitamins, supplemental powders, or snacks. Ensure additional storage seals tightly if carrying liquid and that the capacity of these additional compartments can handle whatever you want them to carry. Hydra Cup’s Dual Threat Shaker Bottle features two compartments, so you can take a pre-and post-workout protein shake with you to the gym.  

Ferriter also suggests keeping an eye out for other functional and practical features: “A carrying handle on top of the lid, easily removable plastic seal in the lid, cup-holder friendly (most are), and a wide mouthpiece that snaps open/closed,” are good features to look for, she says. Plus, bonus points if all pieces are dishwasher safe to make cleanup a breeze.

Why Trust Verywell Fit

Michelle Parente is an experienced fitness writer who is passionate about making great product recommendations. As a wellness enthusiast herself, Michelle believes in a balanced approach and that good nutrition is essential to a successful fitness routine.

Frequently Asked Questions

  • What is the best way to clean a shaker bottle?
  • If your shaker bottle is dishwasher safe, placing it on the top rack can be effective for a deep clean. However, note that strong detergents may taint the taste of the bottle over time. If you’re sensitive to this, it’s better to hand wash your bottle.“Make sure to take out the plastic seal on the inside of the lid if it has one,” says Ferriter. “Those can hold nasty leftover milk or powder from your shakes, not to mention they can grow moldy over time (yuck!). If the bottle is not dishwasher safe, a good scrub with soap and hot water will do the trick.”
  • Are all shaker bottles dishwasher safe?
  • While many plastics used in drinkware are made from durable, BPA- or phthalate-free materials, not all can take the heat of dishwashers. Therefore it’s always best to follow the manufacturer’s directions for cleaning and caring for your shaker bottle. Many will indicate whether it’s safe to run through a wash cycle and specify if it should go top rack.“Most components can be placed on the top rack, except the wire mesh ball that can be washed in the silverware rack,” says Barber. “Note that insulated blender bottles usually are not dishwasher-safe and have to be hand-washed with dish soap and water,” she adds. When in doubt, it’s always best to hand wash.
  • What can I use instead of a shaker bottle for protein?
  • If you don’t have a shaker bottle handy when you need it, there are some make-shift hacks to get you by. Ferriter says that in a pinch, any water bottle will do. “You can also purchase the metal shaker spheres individually and add that to any water bottle to turn it into a shaker,” she says.When at home, a cappuccino milk frother or blender does the trick to smooth shake mixes. Alternatively, some prefer a protein-packed smoothie, albeit slightly less convenient and more intensive. “I prefer a Magic Bullet, myself, instead of a blender bottle,” Barber says.
  • How do I keep a shaker bottle from smelling?
  • To avoid lingering smells or funky flavors, clean the cup, lid, and the blending mechanism as soon as possible after use with dish soap and warm water, and soak overnight if necessary. “Leaving the shaker bottle stuffed in your gym bag or a hot car and waiting until you get home to clean it is going to make it smell—and we all know that stench,” says Ferriter. “If you don’t have access to a dishwasher or sponge right away, shake some soap and hot water in the bottle to clean, rinse, and let air dry. Then fully wash it when you’re home," she adds.
  • How big should my shaker bottle be?
  • Shaker bottles tend to come in a variety of sizes, typically anywhere from 16 to 30 ounces. Choosing what size vessel to purchase depends on how much liquid your powder will require. This is entirely up to personal preference and intended use, says Knott.
  • How much does a quality shaker bottle cost?
  • A quality shaker bottle can cost anywhere from $10-$100, depending on the blending mechanism and intended use. Budget-friendly shaker bottles tend to have a more basic design while still producing a smooth and satisfying shake. More expensive options, like the Blendjet 2, often feature stainless steel blades, allowing you to whip up delicious protein shakes, smoothies, and other blended concoctions in no time.Our best overall pick, GNC’s Pro Performance 28 oz JAXX Shaker Cup is the budget-friendliest option on our list, often available for just $10.

If your shaker bottle is dishwasher safe, placing it on the top rack can be effective for a deep clean. However, note that strong detergents may taint the taste of the bottle over time. If you’re sensitive to this, it’s better to hand wash your bottle.

While many plastics used in drinkware are made from durable, BPA- or phthalate-free materials, not all can take the heat of dishwashers. Therefore it’s always best to follow the manufacturer’s directions for cleaning and caring for your shaker bottle. Many will indicate whether it’s safe to run through a wash cycle and specify if it should go top rack.

If you don’t have a shaker bottle handy when you need it, there are some make-shift hacks to get you by. Ferriter says that in a pinch, any water bottle will do. “You can also purchase the metal shaker spheres individually and add that to any water bottle to turn it into a shaker,” she says.

To avoid lingering smells or funky flavors, clean the cup, lid, and the blending mechanism as soon as possible after use with dish soap and warm water, and soak overnight if necessary. “Leaving the shaker bottle stuffed in your gym bag or a hot car and waiting until you get home to clean it is going to make it smell—and we all know that stench,” says Ferriter. “If you don’t have access to a dishwasher or sponge right away, shake some soap and hot water in the bottle to clean, rinse, and let air dry. Then fully wash it when you’re home," she adds.

Shaker bottles tend to come in a variety of sizes, typically anywhere from 16 to 30 ounces. Choosing what size vessel to purchase depends on how much liquid your powder will require. This is entirely up to personal preference and intended use, says Knott.

A quality shaker bottle can cost anywhere from $10-$100, depending on the blending mechanism and intended use. Budget-friendly shaker bottles tend to have a more basic design while still producing a smooth and satisfying shake. More expensive options, like the Blendjet 2, often feature stainless steel blades, allowing you to whip up delicious protein shakes, smoothies, and other blended concoctions in no time.

Additional reporting by Jessica Murtaugh, CPT

A certified personal trainer and nutrition coach, Jessica Murtaugh, CPT, is constantly researching the latest and best in dietary health, supplements, and nutritional accessories. For this shopping guide, she prioritized quality bottle brands that fit the budget, nutritional requirements, and convenience needs of everyday users looking to stay healthy on the go.