Geissele 13.5" M-LOK MK4 DDC Super Modular Rail 05-278S

Geissele 13.5" M-LOK MK4 DDC Super Modular Rail 05-278S is the ultra-rugged end of Geissele's M-LOK lineup - built with integrated Picatinny sections up front rather than relying on M-LOK for everything, which matters if you're mounting anything that needs a hard rail interface.

Machined from 7000-series aluminum and Type III hardcoat anodized in Desert Dirt Color, this Geissele Super Modular Rail MK4 locks onto the receiver through a 6-bolt interface paired with Geissele's proprietary 2.25" barrel nut. That's longer surface contact than a standard nut provides, which is really the whole reason these rails hold zero as well as they do after you've pulled the handguard for maintenance. Integrated Picatinny sections sit at 3, 6, and 9 o'clock up front, backed by M-LOK slots at those same positions plus the upper 45° quadrants for everything else.

This Geissele MK4 13.5 rail comes in at 11.8 ounces bare, 13.5 with the barrel nut installed - not the lightest option in the catalog, but the added Picatinny real estate up front is the tradeoff, and for a lot of builds that's a fair one.

Key Features:

• 13.5" free-float length, full-length Picatinny top rail
• Integrated Picatinny sections at 3, 6, 9 o'clock
• M-LOK slots at 3, 6, 9 o'clock plus upper 45° quadrants
• 7000-series aluminum, Type III hardcoat anodized
• 6-bolt interface w/ proprietary 2.25" Geissele barrel nut
• Weight: 11.8 oz bare, 13.5 oz w/ barrel nut
• Desert Dirt Color finish
• Fits mil-spec AR-15 upper receivers

If you need hard-mount Picatinny sections instead of relying entirely on M-LOK adapters, this Geissele MK4 DDC rail is built exactly for that - reference Geissele MK4 Rail or part number 05-278S for the black variant and other lengths.