Operating System: PWS Long Stroke Piston System, 3-Setting Adjustable Gas System

Muzzle Device: A2 Flash Hider

Caliber: .223 Wylde

Barrel Length: 11.85”

Barrel: 416 Stainless Steel, Button Rifled

Twist: 1:8

Handguard: PWS free float Mlok™11” Handguard (1.6” width, 2.1” height)

Upper Receiver: PWS Proprietary Piston Upper, 6061 extrusion, Anodized 

Charging Handle: Radian Raptor™Ambidextrous Charging Handle

Overall Length:   20.5”

Height:  2.3”

Width:   2.5”

Weight: 4 lbs. 2 oz.

The MK1 PRO upper will not work with a lower that has extended bolt catch/bolt releases that extends over the upper receiver- like the Phase 5 or B.A.D. style.