This aftermarket Tactical H&K 91, G3 HK Extended Carbine Length Handguard Is M-lok style CNC machined aluminum and compatible with most HK33 variants including HK91 variant with H&K Carbine" sight radius. Comes with U.S. made steel mounting hardware. 3.9 inch rail space forward of front sight Drop-in style no gun smithing required. Picatinny forward top rail and rows of M-Lok for ultimate customization. Each rail system is supplied with two modular top sections, one Picatinny and one M-Lok. Length 14.1 inches.