Ok i got these for one reason #16 0ring on the kayfun V4 ,though i have suffered no leaks i bought just incase i do in the future ,anyway took KF V4 apart and tried a couple of these Orings on for size lol , the few tried fit well , decided id leave one on and put back together see how it goes and no leaks ,i know mine didnt leak before but i know the KF V4 has issues and i thought better safe than sorry and well pass on my experience with these Orings in use with the Kayfun V4 . didnt need this many and would have preferred a large bag of mixed Orings but hey they are cheap and worked for the purpose i bought them for. Hope this may help a few out there . Vape On .