KAC-Knight's Armament URX 4 IBN Keymod Rail 5.56mm 10.75" Length

Knight's Armament
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URX 4 Forend Assembly, 10.75" Length

The KAC URX 4 Rail is a fully modular design that utilizes the revolutionary KeyMod accessory mounting system. The URX 4 Rail is stronger and more stable than previous URX designs due to its one piece construction. It is also lighter due to its Integral Barrel Nut (IBN) system of attachment. The IBN system allows the rail itself to act as the barrel nut when torqued onto the rifle, completely eliminating the need for a separate steel barrel nut. KeyMod accessories may be mounted anywhere along the URX 4’s length, making it one of the most user configurable designs on the market. The URX 4 includes two QD sling swivel sockets, one on the left side and one on the right.


  • Length: 10.75”
  • Weight: 10.2 oz
  • Inside Dia: 1.55”
  • Outside Dia: 1.68” (Side to Side)

Each URX 4 Rail comes complete with an installation wrench, shim kit and instructions. Other lengths available include 8.5", 10", 13", and 14.5".