Super Modular Rails

Super Modular Rail MK4 M-LOK®

Super Modular Rail MK4 M-LOK®

Super Modular Rail MK4 M-LOK®

Regular Price: $225.00

Sale Price $168.75

MK4 Height:


Available Lengths: 

 7"  •   9.5"  •  13"  •  15"

MK4 ID*:




Installed Weight
(w/ Hardware):

7” MK4 Rail - 9.7oz
9.5” MK4 Rail - 11.0oz
13”  MK4 Rail - 14.1oz
15” MK4 Rail - 15.4oz 

ID* - Inner Diameter
OD* - Outer Diameter
DAQ* - Distance Across Quadrants

Available in Black and DDC

.750" Low Profile Stainless Steel Geissele Super Gas Block Included

Click Here to review our DDC (Desert Dirt Color) disclaimer before purchasing.

NOTE: Our rails are designed to work with Mil-Spec M4 upper receivers. The compatibility with billet receiver sets is unknown.


Item Number:



In stock

* Required Fields

Regular Price: $225.00

Sale Price $168.75

Super Modular Rail MK4 M-LOK®

Full Description

The Super Modular Rail (SMR) MK4 M-LOK™ is Geissele’s ultra-lightweight M-LOK option. These rails are purpose-built and feature integrated M1913 picatinny rail sections at the fore of the rail in the 3, 6 and 9 o’clock positions. Maximum venting for heat dissipation also dramatically reduces the rail's overall weight, while maintaining its same strong and rigid platform. Utilizing Magpul's M-LOK technology at the 3, 6, and 9 o'clock positions, as well as the upper 45 quadrants. The SMR MK4 is both versatile and modular, allowing the user to tailor their platform to his or her unique needs.

The SMR MK4 also features Geissele's proprietary 2.25" long barrel nut. This increases the surface contact where the rail interfaces with the receiver and creates a platform that can be trusted to be straight and true the entire length of the free float rail. This increases accuracy and zero repeatability during disassembly and reassembly when performing maintenance.

Bundled with a low-profile Geissele Super Gas Block, a $59 value, the SMR MK4 is not only feature packed, but it is also value packed.


Installation Instructions

Super Modular Rail MK4 M-LOK®

Reviews (9)

overall rating 5.0

+ Add a Review

Only registered users can write reviews.
Please, log in or register.

Excellent Product! - Michael

Purchased a new Norris Arms AR in 6.5 Grendel with a MK4 x 15 Rail over the holidays. Excellent design and beautifully machined rail. 1913 section at the 6 o'clock end position is perfect for your Atlas bipod!

January 20th, 2019

awesome rail! - Christopher

First MK4 in 15" and it feels solid once installed- Used the G gas block that it came with and the upper built came out perfect!

January 7th, 2019

Two thumbs up - Adam

Beautifully machined, not to heavy, mounts up solidly to the barrel nut and is easy to install. If you buy a product that says "Geissele" on it, rest assured you can bet your life on it

November 25th, 2018

Best rail on the market - Adam

If you buy a product from Geissele you can be sure that it is going to be made of top quality. The MK4 is machined to perfection and it is very easy to install as long as you have the proper tools. The toughest part for me was pinning the SGB, highly detailed step by step instructions helped me through that part...The free swag pack was cool and much appreciated, thank you

November 17th, 2018

Great - Nova

I have the 13inch variation on my AR. Looks great. Feels great. Only issue is the MLok at the 6 o'clock position of mine will not accept true MLok fasteners. The holesare too wide. It is not an issue at all because I used the MOE to MLok adapters. Just used the screws and bigger fastener plate and works like a charm. 100% satisfied with it

May 31st, 2018

3 and counting - Justin

Just oredered my third mk4 rail, have them on all my rifles! More to come! Thanks Bill Geissele, and team Geissele!

April 4th, 2018

Lightweight, Durable, Functional - Derald

The MK4 is an outstanding rail providing the modularity of M-LOK with quick attach section for picatinny compatible accessories. The ability to use the rail for the more common accessories such as grips and lights means the rail is functional in the absence of the M-LOK rail sections.

March 31st, 2018

Best rails I've owned - Joelski

I have Mk 4's on two rifles and can't say enough good about them. The 1913 at the end allows ideal placement of my bipod and the M-Lok at 10:30 and 1:30 allow tight-in mounting of your weapon mounted lights. These rails have what I need, where I need it, and nothing I don't need everywhere else. Looking forward to adding a Mk 13 to my next rifle, Thanks for the dependable gear!

November 16th, 2017

MK4 outstanding - Brian

I recently purchased the MK4 9" rail, the quality is outstanding, and the customer service is even better. I'll be buying more. Thanks

June 20th, 2017
Stay Connected.