UTG Universal Single-Rail Barrel Mount with 5 Picatinny Slots.brbrSolid aluminum construction with matte black finish. Smart 2-piece design for clamping rifle barrel. 2.4 inches long and 1.2 inches wide. 5 picatinny slots. Compatible firearm barrel range: .51 inches (13mm) to .78 inches (20mm) in diameter. Easy installation, no gunsmithing required.p