[6 Piece Bottle Cap Set]: Our bottle caps turn any standard water bottle into a leak-proof cup for babies, children and adults. The plug of the bottle adapter fits the bottle opening perfectly, kids can easily drink water without having to suck a lot and you don't have to worry about children getting wet or dirty while drinking. Keep your clothes clean and dry! [Fits 28mm Standard Opening Bottles]: Our bottle cap is perfect for the standard bottle (28mm opening), you can also combine it with a reusable straw that helps protect children's mouth from hard bottle opening. With the help of this silicone water bottle accessory, children will not pour water when drinking from a water bottle. [High Quality Silicone & Easy to Clean]: Our baby water bottle caps are made of food grade silicone material, which is safe, BPA free and dishwasher safe. They are soft and flexible, gentle on your children's mouth and protect them from sharp edges or rough surfaces that could potentially hurt them. [Warm Tips]: Our water bottle caps are leak proof, that is, the cap and bottle opening can be closed well without leaking. However, the bottle cap releases liquid when squeezed, making it easier for children to access water. This is not a quality problem.