Knight's Armament Co URX 3.1 Free Float Rail System for M4 / M16 Series Airsoft AEG Rifles - 13.5" / TanFeatures:Fully licensed by Knight's Armament CompanyMade from CNC milled aluminumMatte black anodized finish20mm Picatinny railsLength:13.5"Compatibility:For Tokyo Marui, Matrix, G&P; and other compatible M4 / M16 Series Airsoft AEG RiflesMaterial:CNC Milled Aluminum