I am so happy I purchase these! I can use the baby bottles for travel or when baby is older and use it as a snack cup. Makes the bottles a great purchase because it grows with baby and has a long use! The cap itself must be used with the ring that comes with bottle. So when you remove the nipple from the ring, attached the cap to the ring and then it fit perfectly on the bottle. The direction are right on the front of the bottle in plain site. The bottom reviewer gave 1 star because the cap didn’t fit, but she might be using it incorrectly, the front of the box states and shows you must attach the cap to the ring. So her review really is miss informing people.
It doesn’t fit so well.