This is a Luth-AR Stock known as the MBA-4 Carbine Stock, model MBA-4-CHP.
Luth-AR's MBA-4 Carbine Stock with Cheek Riser that Fits AR-15 & AR-10 Commercial and Mil-Spec Buffer Tubes is their new revolutionary designed stock. This stock when paired with Carbine AR rifles allows shooters to have full adjustability. It fits all .223 and most .308 AR carbine style rifles. It is a strong and lightweight stock made with super strong glass filled nylon and is easy to replace and quick to install. Features a picatinny rail and a revolutionary anti-rattle set screw.
Features:
Adapts To Existing Commercial and Mil-Spec Buffer Tubes
Fits all .223 and most .308 AR carbine style rifles