Our Silicone Bottles are made from 100% BPA free medical grade silicone. Because silicone is soft and squeezable, it is important to make sure the bottle is assembled properly. To assemble the nipple, pull the silicone nipple up into the screw ring until it locks into place. To assemble the base, align the rectangular bumps along the soft silicone base's lip with the notches on clear plastic screw top. Pull the silicone lip OVER the clear plastic screw top rim. Once both are assembled, gently screw them together until tight. Be careful not to over tighten. Over tightening may cause the silicone base to become misaligned.