Everything else is just a shaker cup. The Blender Bottle Classic revolutionized the industry back in 2004 with its leak proof seal, iconic design, and the Blender Ball 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. The patented mixing system uses the Blender Ball wire whisk found only in Blender Bottle brand shaker cups to mix even the thickest ingredients as you shake. Integrated with the Stay Open 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. The Classic's screw on lid and secure flip cap keep your gym bag and car seat dry. With a snug twist of the lid and the assuring 'snap' of the flip cap, you’re ready to roll.