Everything else is just a shaker cup. The BlenderBottle revolutionized the industry back in 2004 with its leak-proof seal, iconic design, and the BlenderBall® wire whisk. Now, years later, it's still the best-selling shaker on the market. Why? Because it works. Say 'goodbye' to lumpy protein shakes and 'hello' to smooth, great-tasting drinks. Our patented mixing system uses the BlenderBall® wire whisk-found only in BlenderBottle® brand shaker cups-to mix even the thickest ingredients as you shake. Integrated with the StayOpen™ flip cap, the adjustable carry loop lets you hold more when your hands are full and offers a convenient place to attach keys while at the gym. Made from only the highest-quality materials, BlenderBottle® brand shaker cups are-and always have been-BPA and Phthalate free. Workouts and workdays can get mundane, but that doesn't mean your nutrition shakes have to. Add ingredients like peanut butter, applesauce, or yogurt to your protein or meal-replacement shakes for added flavor - the BlenderBall whips them in with ease.