Geissele MK16 Super M-Lok Modular Rail 13.5in Black. Mounted to your AR-15 upper using the updated version of the proven Geissele Barrel Nut design the MK16 is not only easy to install and maintain but offers superior rigidity. Anti-rotation tabs and set-screws ensure that your rail will not rotate even under the most extreme conditions of use. M1913 picatinny rail on top and M-LOK slots on every quadrant ensures maximum customization for all your accessories. The Geissele SMR MK16 is precision machined using 7000 Series Aluminum due to its strong rigid and light properties and is finished in durable Type-3 Hardcoat anodized. Specifications for Geissele Mk16 M-Lok Super Modular Rail: Manufacturer: Geissele Finish: Type 3 Hard Coat Anodized Fabric/Material: 7000-series aluminum Gun Make: AR Platform Gun Model: AR-15 Gun Type: Rifle Handguard Type: Free-Float Gun Rail: Picatinny Inner Diameter: 1.26 in Outer Diameter: 1.59 in Height: 2.39 in Mount Type: M-LOK Country of Origin: USA Package Contents: Geissele MK16 Super M-Lok 9.3in Modular Rail NOTE: IF THIS IS YOUR FIRST TIME PURCHASING A GEISSELE AUTOMATICS RAIL YOU WILL NEED TO PURCHASE A BARREL NUT WRENCH IN ORDER TO PROPERLY INSTALL THE RAIL. Geissele 05-650B: MK16 Super M-Lok Modular Rail 13.5in Black