Geissele 15" M-LOK MK4 Black Super Modular Rail 05-315B

Geissele 15" M-LOK MK4 Black Super Modular Rail 05-315B is as much rail as the MK4 line offers - the pick for anyone running a longer barrel or heavier accessory load who's found the 13.5" a little tight.

Machined from 7000-series aluminum and Type III hardcoat anodized, this Geissele Super Modular Rail MK4 locks onto the receiver through Geissele's proprietary 2.25" barrel nut, which gives it far more surface contact with the upper than a standard nut - the reason these rails hold zero through repeated disassembly instead of gradually working loose. Integrated Picatinny sections sit at 3, 6, and 9 o'clock up front, so lights and lasers that need a hard mount aren't stuck relying on M-LOK adapters even at this length.

M-LOK slots cover those same positions plus the upper 45° quadrants, and aggressive venting on the lower sections keeps weight manageable despite the added length. This Geissele MK4 15 rail comes in at 12.8 ounces bare, 15.1 with the barrel nut — reasonable for a 15" tube built this rigid.

Key Features:

• 15" 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
• Proprietary 2.25" Geissele barrel nut
• Weight: 12.8 oz bare, 15.1 oz w/ barrel nut
• Black finish
• Fits mil-spec AR-15 upper receivers

This Geissele MK4 Rail in the full 15" length is built for shooters who'd rather have too much hard-mount real estate than not enough.