I had a new baby in June, and being my first, I knew nothing about feeding one. I first was using the pre-filled, nipple-ready bottles of formula from the hospital, then moved on to the "ergonomically correct" bottles from Evenflo. I should have stuck with those. My baby doesn't really like the smaller, more traditional sized nipples, so when a friend gave us these Avent Naturally bottles, I figured they were worth a try. In the beginning, there were no problems, but now that I've gone out and bought more, since the baby loves them, all hell has broken loose. They leak all over. All the time. Leak Leak Leak Leak Leak. At first I thought I was too stupid to put the caps on the right way, so I blamed myself and kept on trying. But now that I've recently heard from a few friends that they have had the same problems, I feel a bit smarter. Apparently the caps don't really fit too well on the bottle, and as soon as you shake it to mix the formula, or hand it to the baby, it starts leaking from the seal. All over. I definitely won't be buying more, especially after contacting the company, and only receiving some coupons and no explanation. Stick to the cheap bottles!