The Geissele Super Modular Rail MK16 offers unmatched performance for the most demanding shooters. 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. Geissele DDC" or Desert Dirt Color" refers to the variety of shades of desert terrain. Differing shades of DDC are desired on a military small arm to breakup the outline of the weapon. These colors can vary from color seen in the picture of the product" and can also vary from each other when comparing one product to another product. So it is possible that your accessory rails will not match exactly to your rail.