Geissele 14.5" HK Black Super Modular Rail 05-191B was designed to replace the standard rail on an HK MR556 or HK 416 weapon platform. The rail system utilizes the stock HK barrel nut but incorporates the strength, rigidity, and modularity expected of a Geissele product. This Geissele SMR rail is constructed of billet 7075-T6 aluminum and finished in Type III hardcoat anodize to meet military specifications. It includes 3 M1913 Picatinny accessory rail sections that mount anywhere along the length of the rail at the 3, 6, and 9 o'clock positions, though accessory sections themselves are sold separately. Those sections mount directly into steel inserts, creating a rock-solid steel-on-steel connection rather than threading straight into aluminum, which matters after repeated removal and reinstallation over the life of a build. Trusted by elite units who provided direct input during development, this Geissele HK Rail carries a 1.35" inner diameter and 1.9" outer diameter, keeping a rugged, tactical profile at approximately 16.3 oz. This Geissele Modular Rail is a direct replacement for the factory rail on HK416 14.5" and MR556 16.5" barreled uppers, though sling attachment points on the gas block will need to be removed on HK416 models before it slides on properly. Key Features: 14.5" length (actual rail length 13 5/8") Billet 7075-T6 aluminum, Type III hardcoat anodized 3 M1913 Picatinny sections at 3, 6, 9 o'clock, steel insert mounting Uses stock HK barrel nut for installation Inner diameter 1.35", outer diameter 1.9" Weight: approx. 16.3 oz Black finish Fits HK416 and MR556 platforms This rail brings Geissele's Super Modular engineering to the HK platform, built for shooters who wanted more than the factory rail without giving up compatibility with the stock barrel nut. Geissele 14.5" HK Black Super Modular Rail 05-191B