Our best-selling bottle. the Little Big Mouth 21oz Bottle takes a revolutionary design and shrinks it down a bit. It's conveniently shaped and absolutely leak-proof. It has a tight-sealing Big Mouth screw top that's ultra-wide for adding things like ice or your hydration powder of choice. This piece also provides an incredible level of water flow that's up to 50% greater than the competition. Meanwhile. we gave the bottle a flexible. ergonomic design that grips to cages and fits easily in the hand. while the bottle's construction is made from BPA-free plastic that's 100% FDA food-grade approved.