Geissele Automatics MK4, Super Modular Rail, Handguard, 10.5, M-LOK, Barrel Nut Wrench Sold Separately (GEI-02-243), Gas Block Not Included, Black 05-1656B Versatile and innovative" Geissele's MK4 DDC Super Modular Rail is a perfect addition to any AR-platform. It features a full length picatinny rail with more than enough space for optics" iron sights" and clip-on night vision/thermal devices. Additional forward-mounted picatinny rail segments are located in the 3" 6" and 9 o'clock positions" and numerous M-LOK attachment points towards the rear gives the user the user virtually unlimited customization options in terms of tactical lights" lasers" fore-grips" and other accessories.