I love them! Being a first time mom and tring new things out, We had gone through several bottles and no luck. It was always the case of my daughter sucking in too much air. Then by chance we tried them and have been using them since. We started out when she was about 6wks old and she had no problem going from from breastfeeding to bottle. She was less gassy and did not spit up as soon as she was done from all the air that was sucked in while feeding. Then recently we had started using the Natural Shape bottles and she is able to hold those a lot better as well as drink from the nipple. The only down fall about the bottles are tring to locate replacment vent dics. Since my daughter had started eating cereal in her bottle the cereal settles along the the bottom of the vent disc and in the small vent holes. Even after daily cleaning and rinsing after use they still have a hard time coming clean. But overall they are the best bottles my daughter has used an reasonable priced as well.