The Super Modular Rail (SMR) MK4 M-LOK are purpose-built and feature integrated M1913 picatinny rail sections at the fore of the rail in the 3, 6 and 9 o'clock positions. It also features Geissele's proprietary 2" long barrel nut.
Specifications:

Type	Railed Forend
Firearm Type	Rifle
Firearm Model	AR-15
Material	Aluminum
Finish	Black
Features
Adjustment Type
Positions
Length of Pull
Rails	Picatinny
Texture Type
Swivel Studs
Free Floating
Grip Type
Tube Included
Capacity