The bottles leak! When I complained at Avent's website, the response was that I should use some water around the nipple ring so the seal is tight. What kind of design is that? I've had several occasions where the milk leaked as soon it was tilted to go into the baby's mouth. It is very frustrating when you have to open the bottle and try re-sealing it several times while the baby is screaming. Besides the fact, it is annoying when breastmilk goes waste because of the bottle design. For what you pay for the bottles, I had expected better quality. I would definitely not recommend these bottles to any of my friends.