we use Avent bottle year ago and they leak , they do not have this ring as part of the design . when we have we second child , we try Avent bottle again and thankfully , they no longer leak . until you lose one of these precious ring . I look for these in the store and could not find they . fortunately here on Amazon they be a great price and do just what they should . they arrive quickly and now we do not have any more leaky bottle .