The 28 Oz. Shake & Go® Fit Mixer Bottle from Contigo has a uniquely designed rounded-bottom and weighted shaker ball that work together in order to easily and smoothly mix protein drinks and shakes. This 100 percent leak-proof mixer bottle is also engineered with TasteGuard® Protection to help protect tastes and resist odors. The rounded bottom makes clean up a a snap because it helps reduce clumps common in other bottles. This BPA-free bottle and lid are both top-rack dishwasher safe.