This 40-slot Picatinny rail measures 404.8mm (15.54") in length and 9.5mm (0.374") in height. We offer it in either of two profiles; flat base or a 8.5mm radius base that is specifically designed for rifles like the HK91, G3, Cetme C, ect. Rails are readily attached by welding, drilling and tapping for screws, and/or epoxy. If you are into firearm customization, this rail provides a great starting point by ensuring secure and accurate mounting of optics and various other accessories. These rails have a uniform media blasted finish and are lightly oiled for corrosion protection.