The Super Modular Rail (SMR) MK4 M-LOK is Geissele's ultra-lightweight M-LOK option. These rails are purpose-built and feature integrated M1913 picatinny rail sections at the fore of the rail in the 3, 6 and 9 o'clock positions.Maximum venting for heat dissipation also dramatically reduces the rail's overall weight, while maintaining its same strong and rigid platform.Utilizing Magpul's M-LOK technology at the 3, 6, and 9 o'clock positions, as well as the upper 45 quadrants. The SMR MK4 is both versatile and modular, allowing the user to tailor their platform to his or her unique needs.The SMR MK4 also features Geissele's proprietary 2" long barrel nut. This increases the surface contact where the rail interfaces with the receiver and creates a platform that can be trusted to be straight and true the entire length of the free float rail. This increases accuracy and zero repeatability during disassembly and reassembly when performing maintenance.Bundled with a standard Super Gas Block - The bore of the SGB is machined to closely fit around .750" diameter mounting bosses found on most M4 Carbines and AR-15 rifles.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..750" Low Profile Stainless Steel Geissele Super Gas Block IncludedGeissele 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. Due to the chemical process that takes place during Type 3 Hardcoat, the finish on the product can vary from one