The Foxtrot Mike Products .45 ACP Upper Receiver comes fully assembled and ready to drop on any pistol caliber lower receiver that uses Glock magazines. With its full-length Picatinny top rail and M-LOK compatible handguard, the Foxtrot Mike .45 ACP Upper offers plenty of mounting space for optics and other accessories. A unique interlocking connector between the upper receiver and handguard ensures the barrel nut will not work loose over time. Premium Melonite-finished 4150 carbone steel Button-rifled bore, 1-10" twist Ambidextrous, non-reciprocating forward charging handle Bolt/carrier unit with hard Melonite finish, too Does NOT work on the BRN Mfg: Foxtrot Mike Products