Our daughter was born 16 weeks premature, and our NICU actually started using these with her, as she was having problems with reflux, choking, and aspiration. She is now 9 months old, and she's been on these bottles for around 7, and they work wonders. They keep her from being gassy, help her reflux tremendously, and have helped her aspiration problems. I would highly recommend these bottles to another parent. I've really been very pleased with them. I know many parents say there are too many pieces, I just made sure I had enough bottles to get through the day, and washed them frequently. We have 9 bottles total. I've never had a problem with washing them. And I've never had problems with them leaking.