Mesa Tactical LEO Gen II Telescoping Stock Adapter with Recoil Tube Only, Fits Mossberg 500/590A1/MAV88, 12 Gauge and 20 Gauge, Matte Finish, Black 93160 Use Mesa Tactical's collapsible stock kits and adapters to install AR-15 adjustable buttstocks and pistol grips onto the venerable Mossberg 500 shotgun platforms for the ultimate in tactical shotgun configuration performance. The LEO adapter is the most basic" best-selling model" and features an optimal stock elevation allowing the use of iron sights or even the bead sight. The concept behind the telescoping stock system is simple: the shotgun stock is replaced by an adapter" which attaches to the rear end of the shotgun's receiver and it" in turn" mimics the rear end of an AR-15 lower receiver" into which an AR-15 receiver extension tube can be threaded. The AR-15 telescoping stock and pistol grip can then be reliably attached.