-Mounts on mil-spec sized carbine receiver extension tube (not included) from manufacturers such asColt, Armalite, S&W, LMT, and others (please see the note below)-Supplemental friction lock minimizes accuracy robbing wobble-Sloping cheek weld combines a slim profile with user comfort-Shielded release latch prevents snagging & accidental operation-Premium chrome-silicon lock spring provides positive locking & long service life-Side mounting slots accept optional cheek risers for NON AR15/M4 applications-Removable 0.30" Rubber Butt-Pad offers an anti-slip surface & increases impact protection-Compatible with Magpul ASAP®,ASAP® QD & other receiver-mount sling attachments-Sling Mounts -Rear -Push-button QD swivel sling mount accommodates up to 1.5" swivels (ambidextrous) -Rear/Bottom - 1.25" sling loop Toe - Lanyard hole for custom para-cord rigsNote: There are two basic sizes of M4 Carbine receiver extensions (buffer tubes): mil-spec & commercial-spec. If you have a commercial-spec extension on your rifle, make sure to order #MAG311