I researched these and other bottles before my son was born, as I planned to breastfeed and wanted to avoid nipple confusion. We introduced these at 3 weeks, and my son absolutely loves them! We do have issues with the nipples tearing some which makes feeding difficult since it comes out too fast. That being said, when they aren't torn, they are fantastic! We tried a different bottle, and he absolutely refused to take it. I only wish they had these nipples available in store so I didn't have to wait for them to come in.