DYTAC 10" Gen2 G Style MK4 M LOK FBI HRT Handguard
6061 Aluminum Construction (Anodized Aluminum Process)
Engraved Reailstic Marking
M LOK System Handguard
Universal Threaded Barrel Nut to Fit Both Tokyo Marui / Systema PTW / WE / MWS Profiles
Suitable Tokyo Marui M4 Series Airsoft Electric Gun AEG Rifle / PTW / MWS Gas Blow Back GBB Rifle (Fit For Airsoft Guns only)

The Mk4 rails feature the tried and true double-locking screw that secures the rail against the barrel nut and given the MLOK offering these rails have been a huge hit in the real firearm market.  Particularly since the 10" version was made especially for the FBI HRT or SWAT units, and have been heavily sought after as a result.