Knights 12" Free Float RAS MK12 Mod1 Quad Rail

Knights Armament
(9 reviews)
Current Stock:

Knights 12" Free Float RAS MK12 Mod1 Quad Rail


The Knights Armament Free Float RAS has more than proven itself on the battlefield; famously used on Naval Special Warfare Command's Mk12 Mod1 special purpose rifle. The RAS (Rail Adapter System) features full length 12-inch mil-spec M1913 picatinny rails at the 12, 3, 6, and 9 o’clock positions, making it compatible with a variety of rail-mounted tactical accessories. The rail free floats the barrel, allowing for consistent barrel harmonics upon firing, and increased accuracy potential.

The Knight's Free Float RAS is compatible with rifle, carbine and mid length gas systems and requires use of a low profile gas block. Disassembly of the rifle’s gas system and removal of the factory barrel nut will be necessary. This forend uses a proprietary barrel nut that may be installed using a standard AR-15 armorer’s barrel nut wrench (sold separately). For AR15 / SR15 based platforms only. Installation instructions are included.

Includes three KAC 11 Rib Rail Panels.


  • Free Float
  • Installs in minutes
  • Four MIL-STD Picatinny rails at 12, 3, 6, and 9 o'clock
  • Includes 3x Rail Protection Panels
  • Compatible with carbine, mid or rifle length gas systems


  • Weight: 1< lb
  • Length: 12"
  • Machined from 6061/T651 Aircraft Grade Aluminum
  • Mil-Spec hard coat anodized

NSN: 1005-01-562-0913


  • 5
    Knights 12 free float RAS MK12 mod1 quad rail

    Posted by gilberto rodriguez on 19th Aug 2020

    They had the rail I needed for the best price, I received the rail a few days after ordering it which is amazing considering the pandemic currently going on. Definitely will buy. Rom them again.

  • 5
    MK12 reality

    Posted by Ben on 3rd Aug 2020

    I searched everywhere for this real for my clone build either it was out of stock or too expensive. Arms unlimited came through with a great price and great shipping. Good stuff

  • 5
    It’s worth it !!

    Posted by Roberto DerequesensNieves on 25th Jun 2020

    Great service, fast shipping and a great product

  • 5
    Awesome product and service!

    Posted by Donski on 8th Jun 2020

    Best experience ever! The item was nicely packaged and shipping was fast despite of the covid19 issue. Thank you I'll be back for more item 😊

  • 5
    Knights Armament

    Posted by Brett H on 23rd May 2020

    What can I say it's a knights armament product fast shipping absolutely love it.

  • 5
    KAC FF RAS Mk12 Mod 1

    Posted by Derek Shaull on 9th May 2020

    Rail is exactly what I was expecting. Fantastic quality (as is expected from KAC). You will not be disappointed with this rail and it is quintessential for a Mk12 Mod 1 build.

  • 5
    Great overall experience

    Posted by Michael T on 29th Apr 2020

    Just recently purchased the Knights Armament 12inch RAS and overall everything was great! Great quality, great customer service, and best pricing! I will be buying from here for all my next builds

  • 5
    Great Price and Fast Shipping

    Posted by David E on 6th Jan 2020

    Item arrived as described and quickly. Exactly what you need for a Mk12 Mod 1 clone build.

  • 5
    Quick Shipping, Awesome Product

    Posted by Will Boughton on 26th Feb 2019

    Rock solid construction as to be expected from Knight's. RAS is labeled PN 21318 for those that are curious. Very quick shipping, from order to door in 3 days in CA.