The Geissele Super Modular Rail MK4 M-LOK free float handguard for AR-15 is built for shooters who demand a lightweight, rigid platform without sacrificing modularity. Geissele engineered this handguard around purposeful venting that sheds weight while maintaining the structural integrity you need for repeatable zero and tight accuracy. Whether you're running a precision rifle or a duty carbine, the MK4's aluminum construction and free-float design keep your barrel free from stock pressure, letting your setup perform the way it should.
What sets the MK4 apart is its thoughtful hybrid design. You get integrated M1913 picatinny rail sections at the 3, 6, and 9 o'clock positions up front—perfect for mounting lights, lasers, or backup sights where you need them most. Behind that, Geissele's M-LOK slots run along the 3, 6, and 9 o'clock positions and upper 45-degree quadrants, giving you the modularity to attach accessories exactly where they work best for your grip and shooting style. No rail clutter you don't need, no blind spots where you can't mount gear.
Installation is straightforward with Geissele's proprietary 2.25-inch barrel nut, which dramatically increases surface contact between the handguard and receiver. That extended interface means your free float rail stays straight and true through disassembly and reassembly—critical if you run your gun hard and want your zero to track. Note that you'll need a Geissele barrel nut wrench (sold separately) for installation, so plan accordingly if you're building from scratch.
At just over 15 ounces, the MK4 keeps your rifle balanced without forcing you to choose between weight savings and capability. It's the handguard for builders who know exactly what they're mounting and refuse to compromise on quality or precision.
| Length | 15 inches |
| Inner Diameter | 1.35 inches |
| Outer Diameter | 2.11 inches |
| Height | 2.4 inches |
| Weight with Hardware | 15.1 ounces |
| Mounting System | M-LOK and M1913 picatinny |
| Material | Aluminum |
| Barrel Nut | Geissele proprietary 2.25-inch (included) |
You'll need a Geissele barrel nut wrench, which is sold separately. Check with your dealer or contact Geissele directly for the correct wrench for the proprietary 2.25-inch barrel nut included with the MK4.
Yes, the Geissele Super Modular Rail MK4 M-LOK is designed for standard AR-15 platforms. It features a free float design and comes with the proprietary Geissele barrel nut for secure installation on your receiver.
The MK4 comes with the aluminum handguard and the Geissele proprietary 2.25-inch barrel nut. The barrel nut wrench required for installation is sold separately.
Yes. The MK4 features integrated M1913 picatinny rail sections at the 3, 6, and 9 o'clock positions for direct picatinny mounting, plus M-LOK slots at the same positions and upper 45-degree quadrants for M-LOK accessory attachment.
Geissele Automatics
Geissele Automatics
