The MOE slot system was released by Magpul in 2009 as a feature on their MOE handguards, and at the same time compatible accessories such as Picatinny rail sections, direct MOE mounted light mounts, grips, bipod studs, etc. Though newer M-LOK accessories can be used on older MOE slot handguards if an adaptor plate is used, there is no adaptor available for using older MOE accessories on the newer M-LOK handguards.Ī prototype of the MOE slot was revealed by Magpul in late 2007 together with their Masada Concept Rifle (which would later be known as the Adaptive Combat Rifle). The M-LOK system can be seen as an evolution of the Magpul Original Equipment (MOE) system, but the two are not fully compatible. Compared to the Picatinny rail system, both M-LOK and KeyMod enable the user to have a slimmer, lighter, smoother and more fenestrated handguard/ fore-end with accessories mounted only where needed, whereas a Picatinny handguard typically will have rail slots for its whole length resulting in a heavier and bulkier handguard with sharp edges and poorer barrel ventilation. M-LOK allows for direct accessory attachment onto the "negative space" (hollow slot) mounting points, and is a competing standard to VLTOR's open sourced KeyMod system for replacing the ubiquitous Picatinny rail in some applications.
M-LOK, for Modular Lock, is a free licensed firearm rail interface system developed and patented by Magpul Industries. A STNGR USA 15 in (381 mm) HWK M-LOK handguard on an AR-15