The Geissele MK4 Super Modular Rail (brand part no. 05-278B) is a 13.5-inch, black M-LOK handguard built as Geissele’s ultra-rugged option for rifle-length AR builds. The rail is purpose-built with integrated M1913 Picatinny rail sections at the fore in the 3, 6, and 9 o’clock positions, and this rifle-length version ships with Geissele’s proprietary 2-inch-long barrel nut for a straight, true fit at the receiver interface. It installs as a drop-in handguard, giving builders the same rugged Geissele platform in a longer footprint suited to full-length rifle uppers.

Key Specifications

• Measures 13.5 inches in length.
• Built as Geissele’s ultra-rugged MK4 option.
• Features integrated M1913 Picatinny rail sections at the fore, 3, 6, and 9 o’clock.
• Includes M-LOK slots for mounting accessories.
• Includes Geissele’s proprietary 2-inch-long barrel nut.
• Barrel nut design keeps the rail straight and true at the receiver interface.
• Installs as a drop-in handguard.
• Maximum venting reduces weight while aiding heat dissipation.
• Finished in black.

Frequently Asked Questions

Does this rail include a barrel nut? Yes, it ships with Geissele’s proprietary 2-inch-long barrel nut.

Is this rail a drop-in installation? Yes, it installs as a drop-in handguard.

Buy the Geissele MK4 Super Modular Rail

Get a rugged, rifle-length rail built for a straight, true fit. Order it from our Geissele Automatics lineup of AR handguards for fast shipping from our Lubbock, Texas gun shop.