This jig is for SOTs to be able to accurately drill the 3rd hole into an AR lower receivers to convert them from semi automatic to fully automatic. If you are not a SOT you can still legally purchase this jig but you cannot use it to drill the 3rd hole. Some things you can use is for is checking the spec between your safety selector hole and rear takedown pin hole, a keychain, a paper weight or a neat conversation piece.

M-16 Drill Jig