Luth-Ar Ar-15 Mba-3/Mba-4 Carbine Castle Nut
Luth-Ar Ar-15 Mba-3/Mba-4 Carbine Castle Nut, FITS: The Luth-AR Carbine Lock Ring/Castle Nut for MBA-3 and MBA-4 Carbine Buffer Kits, as well as any Mil-Spec or Commercial Carbine receiver extension. Mfg: Luth-Ar