The aggressive thread cap creates a leak proof seal. The threads slope downward on the top and remain flat on the bottom so when the cap is in place there is no room for flex. The Tritan material improves durability and is also BPA free. The cap is made with a stainless steel cover which helps to shockproof the bottle from drop damage. The bottle itself has an oval shape with textured surfaces on each side which allows for a more natural and effortless grip. This unique bottle shape ensures the XT Bottle sits more comfortably against your body while in vest or pockets.