5KU 3 Slot Rail Section QD MLOK
 
There are two spring-loaded wedges in the base of the mount 
When you press the accessory rail section down in the M-LOK slot, two tiny deployment triggers get pressed against the rail firing the wedges into place
20mm Picatinny rail for accessories like foregrip, flashlight and laser sight
suitable for 3.5cm M-LOK Handguard Slot