The Catalyst Arms patent pending HARDPOINT L.O.P. (Length of Pull) spacer, features a rear sling and accessory attachment for the PC Carbine which includes an ambidextrous, integral push button QD sling attachment point. Simply replace or add our spacer between the butt stock and butt pad and the rear sling attachment is ready for use. Machined from 6061-T6 Aluminum - hard coat anodized in matte black.