Geissele Super Modular HK 416 rail Dark Earth REPRO The Geissele Super Modular HK 416 rail was designed to replace the standard rail on the HK 416 weapon platform. Constructed of precision machined, 6061-T6 aluminum allows the SMR HK to incorporate strength, rigidity and modularity while utilizing the stock HK barrel nut. Finished in Type 3 Hardcoat Anodize to meet military specifications and able to use rail sections at the 3, 6 and 9 o’clock positions to mount accessory rails, using steel inserts for a rock solid, steel to steel connection; the SMR HK is trusted by our Nation’s elite warfighters, whose direct input and feedback allowed us to develop the feature and performance rich SMR 416.