ARS Rail System

(5 customer reviews)



The F4 Adaptive Rail System (ARS) is a purpose-built rail combining the functionality of the M1913 Picatinny rail and the adaptability of Magpul’s MLOK system. The ARS handguard features both, maintaining a seamless low profile and versatile configuration. Our Patent Pending MLOK and Picatinny hybrid system is directly integrated into the extruded profile of the rail, rather than a bulky quad rail configuration. No more adapter rails; accessories are attached directly to the rail. Strategic machining allows for maximum venting, air flow, and weight reduction while maintaining the structural integrity to maintain accuracy and repeatability. The barrel nut features an anti-rotation design. This modular system allows the flexibility to configure the rail based on the end-users individual preferences.


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   Technical Specs:

  • Material: Aerospace Grade 6061 T6 Aluminum
  • Functionality: Compatible with M-LOK and M1913 Picatinny accessories without the need of rail adapters.
  • Quick-Disconnect (QD) ports (2)
  • Length: 6.5, 9, and 15.5 inches
  • Finish: Type III Hard Coat Anodized
  • Additional M-LOK slots at (2) 45° Positions for forward mounting lights, lasers, etc.
  • Extended Rail Section at 6 o’clock position at forward section of rail to accommodate slide on Bi-Pods
  • Barrel Nut Diameter:  1.378″
  • Barrel Nut:  7075 Aluminum Type III Hard Anodized Clear
  • Anti-Rotation Tabs
  • 17-4PH Cored Stainless Steel Rail Mounting Attachment – Patent Pending by CMT
  • Weight: 12.8 ounces (15.5″),  8 ounces (9″), 6.4 ounces (6.5″)
  • Made in America with American Metal

**** The measurement for the rail was taken at its longest point, which is the bottom.  The top of the rail is 5.75″ (6.5″ version), 8.3″ (9″ version),  and 15″ (15.5″ version)


Additional information

Weight 2 lbs
Dimensions 20 × 5 × 5 in
Handguard Length

6.5" ARS, 15.5" ARS, 9" ARS

5 reviews for ARS Rail System

  1. GJ

    This rail has been great. Fit and finish are great; it was a little snug going into the barrel nut but that’s better than too loose. Once tightened this rail is solid. Customer service was top notch, all my questions were answered very quickly even before I purchased the rail. The flat black finish matches my Saint perfectly and all the machining is great; no sharp edges but still has crisp lines. All my accessories fit onto the picatinny slots great (I’ve had other rails where this wasn’t the case). Overall a great product and great people.

  2. Jayson Weiner

    Can’t say enough about this rail system. It’s very well thought out and the fact that you get a quad rail in a slim recessed rail is great for attaching accessories. Only knock is waiting for them to get back in stock

  3. Johnnie Steiert

    Perfect rail. fit and finish and mounting system amazing.

  4. Link (verified owner)

    Just got this rail in and still as impressive as when I first saw it last year at a show.
    It’s a well thought out design and gives options no other rails have.

  5. Aj

    Bought one for an ar9 pistol build. One of the best-looking and well made handguards I’ve ever purchased.Plus the thing looks cool. Before I bought it I called F4 to ask them questions and they were really good about answering all of them. Great customer service.

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