9,10,12,13.5,15'' inch ultralight keymod handguard rail mount system purple anodized fit ar-15/m4/m16 .223/5.56

model no. : nsr-9 / nsr-10 / nsr-12 / nsr-13.5 / nsr-15 //length choice : 9'' (230 mm ) / 10'' ( 255 mm ) / 12'' (305 mm ) / 13.5'' (344 mm) / 15'' (382 mm ) //material : t6 6061 aluminum //color : purple anodized ( a little difference is acceptable due to different screen monitor ) //barrel nut thread spec.: 1-1/4-18 unc //barrel nut inside hole diameter: 1.02 in (26 mm) //barrel nut outside diameter: 1.35 in (34.4 mm)