Please note* Sam Yang has two different types of barrel threads, M16x1.5 and 5/8x18. Best way to determine which threads you have is to go to a hardware store and pickup one of the bolts. If the bolt does not screw on then it must be the other size. If your barrel is too close to the fill probe you will need to get the extended adapter version. I currently do not have the short version of the 5/8x18.