I am switching back to Avent bottles. I had switched to Dr Browns since my son has reflux and was spitting up constantly. I don't see that they make a difference so would like to go back to Avent. I have the level 2 and 4 nipples but can't find any level 3's in stores and so would have to order them from Avent online. Isn't it odd that Target and Babies R Us don't carry this size?? Am I missing something? I tried the level 4's but he was choking on the milk so he clearly is not ready for the fast flow nipple.