maymom dome caps compatible with avent natural bottles, avent pp bottles or natural glass bottles; not for avent classic dome; not original avent replacement parts maymom these parts are after-market parts made by maymom, not original philips avent parts. <p> <b>note: </b> due to variations in the size of the existing avent natural screw rings on the market, maymom's dome might not fit tight when you just receive the package. however, after the first sterilization, it will fit correctly and tight. <p> you are buying products that are made by maymom. maymom is not affiliated with philips.