These bottles are awesome. They're easy to use and baby loves them. My only complaints are that you have to be careful when releasing the air from the nipple or milk can come out of sides of the milkbag. I believe that is operator error. When my baby is almost done, the nipple colapses because there is no air inside. That is the bigger complaint. He was able to grip and hold this bottle because it's lightweight and the shape helped. It reminded me of him gripping breast during breastfeeding. (He was 10 wks when these arrived.) So far I really like these. I may have to update after weeks and months of use.