The Troy Industries Pro Grade Rifle Sling Adapter enhances M4 stock reliability by sliding over the existing receiver extension, eliminating the chance of castle nut rotation. The Troy PGRSA allows the addition of an ambidextrous Quick Detach. swivel attachments without modifying the rifle. Constructed of hardened aircraft aluminum with a stainless push down button Quick Detach. swivel, this sling mount installs in less than two minutes with no gunsmithing required. Available in Black and Flat Dark Earth.