The Super Modular Rail (SMR) MK4 M-LOK is a lightweight and versatile rail system designed by Geissele Automatics. It is made from high quality materials and features a number of innovative design features. One of the most notable features of the SMR MK4 M-LOK is its integrated M1913 Picatinny rail sections at the 3, 6, and 9 o'clock positions. This provides a solid platform for mounting accessories such as lights, lasers, and sights. The SMR MK4 M-LOK also features maximum venting for heat dissipation. This helps to keep the rail cool and prevents it from becoming too hot to handle. In addition, the SMR MK4 M-LOK utilizes Magpul's M-LOK technology at the 3, 6, and 9 o'clock positions, as well as the upper 45 quadrants. This allows you to attach a wide variety of accessories to the rail using M-LOK compatible hardware. Another key feature of the SMR MK4 M-LOK is its proprietary 2.25 inches long barrel nut. This increases the surface contact where the rail interfaces with the receiver and creates a platform that is 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.