I should have listened to the reviews. I tried these bottles after using the Platex bottles with disposable liners. These gave my baby more gas! They also leak! Also, Beware! These bottles only reduce gas if you fill them to the top! It is also true that the ink on the bottles rub off. Don't waste your money! Buy the Playtex bottles with liners if you are concerned about your baby having gas! These are not as effective!