This adapter is made from alloy steel and allows you to attach 5/8”-24 threaded suppressors to a 15-1mm threaded muzzle. Adapter has a 7/16” (.437”) thru hole, is 1 1/4” long, 3/4” in diameter and has 11/16” wrench flats. All machined diameters and threaded diameters are concentric with in .001".