my little boy is 7 weeks old he was 4 1/2 months premature, I discovered these bottle because he has really bad colic ,on research these bottles came up and so far i have order and received 2x 5oz bottle and the medium flow teat and I’ve re-order an additional 2x5oz bottle awaiting to come. omg i love these bottle but most of all my little one absolutely love these bottle he actually drinks a lot more from them ,his colic is better and he throws up less, the medium flow suit him best rather than the slow flow, the nipples fit his mouth nicely and the bottle is the perfect size. As for why i like these bottle apart from helping my baby, they are easy to clean, i love the shape and the feel of them, they warm up quickly, the only minor problem i have is sometime it hard to take the lids off but i think its more of a user error that a fault. I would recommend these bottles hands down.