Above is a video showing how the Mace Leak Resistant Nipple works and then the final look of the Leak Resistant Nipple. Many baby bottle nipples on the market today are susceptible to leaks. Baby bottle nipples that leak can cause a mess and waste milk or formula. Our BPA free, pure silicone nipple is by far the best and smartest choice for the parents to make. The nipple is designed to help prevent too much liquid flow from the bottle.