This Shake & Go FIT shaker by Contigo has a unique round-bottom design. Making it easy to mix protein drinks and shakes. Cool looks, convenient features. The Shake & Go FIT has a rounded bottom and weighted shaker ball that are smartly engineered to work together to help reduce clumps and build up that are common in other bottles. The bottle and lid are dishwasher safe (top-rack). These shakers are 100% leak proof and also feature a convenient carrying loop.