The Underworld Arms PS90 M-Lok handguard is 6.5" long and is machined from T6-6061 with a black anodized finish and includes a removable 2" black anodized blast deflector. The handguard includes a black oxide 304 SS barrel nut.
The UA PS90 M-Lok handguard mounts to the barrel using a method that takes inspiration from an AR15 style barrel nut. The handguard nut has 4x 8x32 holes positioned for set screw to lock into the grove cut into the barrel.
To install the handguard slide the barrel nut onto your barrel up to the receiver with the long side of the nut facing down. Apply thread locker to the four 8-32 set screws and tighten them down. Slide the handguard over the nut and apply thread locker to the four 8-32 pan head screws and tighten them down.
Inside Diameter- 1.52"