These bottle were purchased for me as a gift and I ended up getting rid of them after using only two. The angled top is supposed to help with gas in the infant, so they do not get as much gas from drinking from the bottle, but this bottle actually made the problem worse for my daughter. Also, they are not very durable. My first bottle from the pack was dropped after the second use and it cracked on impact. I did not purchase these bottles again after the first package I received. Leak Prevention The leak prevention part is the where I would give the highest score for this bottle and the score is still low. While this aspect was better than a lot of other issues with the bottle, it still leaked way more and sooner than any other bottle I used when she was a baby. Ease of Cleaning I never actually felt as though this bottle was really clean. No matter how many times I cleaned them, there always seemed to be an odd smell in the bottle, which definitely aided in my decision to not purchase them again.