My son is 5 months old. He had colic for 6 weeks as a baby, gas that has persisted currently, acid reflux since 2 weeks, not an easy baby to say the least. I breastfed for 3 months, had to supplement too. My son always took a bottle fine, besides the fact that everything was too fast for him, the nipple flow. He would choke and make crazy noises and spit up a ton. A lot of that was because of his reflux. He's been on medicine for that since two weeks old, Zantac 3x a day, didn't work, spitting up everything.. Now on prolisec 2x a day, doing pretty good, still spitting often. We tried every type of bottle, seriously... Avent, Tommee tippee, Lansinoh, mam, and most currently and for he longest been on dr brown bottles, with a preemie nipple which has been great, but still spitting. I went to a baby fair a few weeks ago and got a gift bag with lots of stuff, in there was two evenflo Classic bottles, one 4oz one 8oz. Gave my son the 4oz evenflo only because he's been trying to hold his bottle and I thought the 4oz would be easier for him to learn. Anyway, I was only doing it to help him learn to hold a bottle, and become more familiar with things, absolutely not thinking about the spit up because honestly if dr brown bottles didn't do the trick I didn't think anything would. I used the 4oz and he drank it so good, so I thought I'd try the 8 oz just to see if it would be okay. I was mainly concerned about it not being vented, I didn't want him to get more gas. Coincidentally he has done amazing and hardly ANY spit up, it's crazy. I'm sorry it was so long, but I just wanted everyone to know that you don't need to buy the most expensive products to have quality. These bottles I would recommend! Here's a pic, if anyone is interested!