The set is pre-assembled and can be easily mounted with any K2 rail. The M K2 insert nut locks itself and can be moved by applying light pressure to the cylinder head screw in the rail. Set consists of: 1 middle clamp XS, aluminum, mill finish/black anodized, 1 cylinder head screw with hexagon socket M8, stainless steel A2, 1 M K2 insert nut with mounting clip (1001643), stainless steel and PA, 1 locking washer S8 (1000473), stainless steel A234-38 mm mill finish