The BlenderBottle Classic revolutionized the shaker cup industry 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. The patented BlenderBall — found only in BlenderBottle shaker cups — whips around inside the bottle as you shake, delivering industry-leading mixing. Add ingredients like peanut butter, applesauce or yogurt to your protein or meal-replacement and the BlenderBall whips them in with ease. Made from the highest-quality materials, BlenderBottle brand shaker cups are, and always have been, BPA- and phthalate-free. The StayOpen flip cap and adjustable carry loop lets you hold and offers a convenient place to attach keys while at the gym. The Classic's screw-on lid and secure flip cap keep your gym bag and car seat dry.