From the manufacturer's site: "Avent has the only bottle that is clinically shown to reduce colic. Plus, the soft, naturally shaped nipple encourages baby to latch on in a way that is similar to breastfeeding. No matter if you choose reusable bottles or the new Tempo Disposable System, you can rest assured you are giving baby the very best with the flexibility you deserve" We received a ton of Avent bottles for our shower and as gifts. So when the girls were born we thought we had the bottle situation sorted out. That is until we discovered that the Avent bottles had a tendency to leak. At first just a minor nuisance, but as time went on the leaky bottles became a real issue. The leak comes from the threads where the ring lid attaches to the bottle. I have read that this can be due to over tightening of the righ lid. Though in my experience, the leaking occurs when the bottle and the ring lid are not completely dry. Seems like it would b easy enough to keep them dry, but it isn't. We ended up switching to Playtex Ventair bottles and have been much happier.