Bought and used these with my son because I liked that they vented air out of the bottle to eliminate a gassy, painful tummy. They seemed to work pretty well at eliminating air from the bottle, but I had many other issues with this nipple system. After a couple months of use and washing, they started leaking where the nipple was attached to the ring. For the price, I would have expected they would have lasted much longer. Also had problems with the vent air bottom, LOTS of leaking after a couple months of use. Not very happy with this product and really not happy with all the messes that resulted from this product. Won't be using this nipple with my next baby.