For a number of years following the end of the Assault Weapons Ban in the United States, the Picatinny rail system was the only viable option for the AR-15 weapon platform. While the Picatinny system allowed for the attachment of various accessories, the rail system was overly bulky and added considerable weight, which created concern for rifle owners increasingly on the go. This left the door open for innovation, and over roughly the last decade, the bulk of the AR-15 rail systems have shifted to the more modern Keymod or MLOK rail attachment style. While both of these options allow for accessory attachment directly to the rail, as well as making the overall weight of the weapon considerably lighter and less bulky, they have some important differences that a discerning gun owner should consider before committing to a new AR-15.

Keymod vs MLOK System - Differentiating Factors

Surprisingly, there is very little difference between MLOK and the KeyMod rails on the surface. The MLOK, or modular lock, was developed by Magpul in 2014. It uses T-nuts and rectangular slots that make the attachment to the rail quick and secure. These T-shaped nuts are placed into the slot, turned, and then lay across the slot, locking them in place. MLOK more closely resembles the Picatinny system because this rail system uses compression force to hold items in place. The MLOK system also offers a dual-point attachment platform that allows for accessories such as lights and foregrips to be mounted with a lot of flexibility for personal preference and comfort. MLOK systems are designed to get the most output from the least amount of material. This helps with weight, but it also helps to reduce the cost, making it a popular choice for budget-conscious shooters. The final benefit to make note of, Magpul’s choice to make the designs open-source, allowing designers, engineers, and arsenals everywhere to produce parts and accessories for it without the need for an adaptor.

Alternatively, KeyMod is named after the shape of its slots, which look like a keyhole. These rail systems work by using conical lugs and key-shaped holes, and they secure a rail system in addition to a multitude of accessories directly to the handguard itself. Simply put the accessory's lug in the opening and slide forward, using a wrench to tighten it up. The slots and lugs face the muzzle, which helps to ensure they don't fly off from the recoil of the firearm. The KeyMod system is a lightweight, modular attachment that only requires you to deploy a rail section large enough to mount the hardware you need. Additionally, all of its angles and cuts are in the interior of the handguard, allowing for more comfort without needing to have rail covers mounted.

MLOK Rail Accessories Overtaking Market Share

During testing for the Advanced Sniper Rifle Programs, MLOK accessories performed at a higher level than Keymod on a regular basis. Due to its reliability and ease of use, it was selected for use on the Suppressed Upper Receiver Groups for military use and soon became a more popular option in the civilian market as well. While there are still many Keymod systems in use today, the availability of accessories has started to dwindle over the last few years as the bulk of new AR-15s produced has now opted to go with the MLOK system. 

Rail Accessories For All Types

RailScales offers rail covers, as well as many other AR-15 accessories for both the MLOK and the KeyMod systems, so no matter customer preference, RailScales has an option to enhance the function and aesthetic. Where many companies have opted to discontinue their Keymod accessory options, RailScales continues to make products available for multiple attachment platforms, and even uses their COG multi-mount system to make moving certain accessories from Keymod to MLOK seamless. 

RailScales Compatibility Across Rail Systems

While the M-LOK and KeyMod systems both changed how shooters interact with the AR-15 platform, RailScales has built products that support either option without forcing a compromise. Their innovative COG™ Multi-Mount System allows certain accessories—like the Karve® Handstop and Anchor® Vertical Grip—to be installed interchangeably on both M-LOK and KeyMod rails.
This ensures that owners of legacy rifles aren’t left behind while those running the latest platforms enjoy seamless, hardware-mounted control accessories.

RailScales’ continued support for KeyMod rails is notable; where most manufacturers abandoned the format, RailScales recognizes that countless rifles are still equipped with KeyMod systems from BCM, Daniel Defense, and early Geissele platforms. For those users, HTP® Scales (High-Temp Polymer) and G10 RailScales remain the perfect lightweight, heat-resistant upgrade for comfort and grip retention.

For shooters running M-LOK, RailScales’ XOS-H® Panels and RSB-M® Stubby Vertical Grip provide modern compatibility and modular performance, integrating with compact PDW-style builds and larger carbines alike.

Material Innovation and Heat Management

A primary benefit of both KeyMod and M-LOK systems is reduced weight—but thinner aluminum rails transfer heat faster. To combat this, RailScales engineered their namesake G10 and HTP® rail covers, offering both heat mitigation and texture-driven grip enhancement.

• G10 Scales: Machined from industrial FR-4 composite for maximum durability and minimal weight.

• HTP® Polymer Scales: Injection-molded for cost efficiency and available in multiple colors (FDE, Sniper Grey, OD Green, Black).

• XOS-H® Panels: Three-sided coverage and accessory cutouts for laser and light integration without sacrificing grip or airflow.

The result is a cooler-running, more controllable rifle—particularly beneficial during rapid strings of fire or suppressed use, where rail heat is most noticeable.

Choosing Between M-LOK and KeyMod: What Really Matters

Both systems will reliably hold accessories in place, but M-LOK’s widespread adoption has made it the modern standard. For new buyers, the availability of mounts, light adapters, bipods, and sling points is greater with M-LOK.
However, if you already own a KeyMod rail, there’s no functional reason to abandon it—especially since RailScales continues to produce compatible accessories.

FAQ — Understanding M-LOK vs KeyMod and RailScales Support

Q: Can I use RailScales products on both KeyMod and M-LOK rails?
A: Yes. RailScales’ patented COG™ Multi-Mount System allows several of their accessories, such as the Karve® Handstop, to attach securely to either rail type.

Q: Why did M-LOK overtake KeyMod?
A: M-LOK demonstrated superior performance during military testing for durability and return-to-zero. Its dual-point attachment and open-source design led to broader manufacturer adoption.

Q: Are KeyMod accessories still worth buying?
A: Absolutely. Many rifles in service still feature KeyMod rails, and RailScales continues to support those users with compatible products.

Q: What’s the biggest advantage of RailScales G10 panels over polymer covers?
A: G10 panels handle high heat, provide improved traction under sweat or rain, and maintain a slim, precision-machined feel that polymer often lacks.

Q: How do I know if my rail is M-LOK or KeyMod?
A: M-LOK slots are rectangular, while KeyMod slots resemble keyholes with rounded rear sections. If unsure, RailScales’ customer support can help confirm compatibility before purchase.

Q: Which RailScales products offer the most versatility?
A: The Karve® Handstop and Anchor® Grip provide dual mounting options, while the XOS-H® Panels fit most modern M-LOK rails and accommodate accessory cutouts for lasers and lights.

The transition from the Picatinny system to modular KeyMod and M-LOK rails marked one of the most significant evolutions in the AR-15’s history. As the industry continues to favor lightweight, modular platforms, RailScales ensures that shooters—old and new—retain access to heat-resistant, ergonomic, and durable rail accessories that fit any setup.

Whether you’re maintaining a legacy KeyMod rifle or upgrading to a modern M-LOK build, RailScales stands as one of the few companies committed to both systems equally—offering function, form, and forward-thinking engineering that keeps your rifle balanced, cool, and ready for the range.

 

Disclaimer:

This blog content was generated by a human and with the aid of artificial intelligence. It may contain errors or inaccuracies and should not be relied upon as a substitute for professional advice. This content is for SEO/entertainment purposes only and the views expressed in this content does not necessarily reflect the views of RailScales LLC. For more information, please refer to bullet point #13 on our FAQ.