This is a CMMG Barrel chambered in 5.7X28MM, model 57DF1C7.
Great choice for your PS90 SBR project. Pair this with a CMMG PS90 Flash hider or thread adapter to complete your SBR.
Features:
10.4";4140 Chrome Moly;Salt Bath Nitride Finish;1:9 Twist;5.7×28 Chamber;Threaded M12x1.0 LH