This is a TROY Rail known as the Alpha, model STRX-AL1-11BT-01.
Building off of the patented TRX Extreme design that revolutionized rail-based handguards" the Alpha Rail utilizes a new" low-profile locking mechanism and affords unparalleled strength and stability. Comes with two 2" and one 4.2"detachable rails and all mounting hardware but the barrel nut is not included.
Features:
Black finish
11 Alpha BattleRail;Free floating;Low profile;Machined from hardened aircraft aluminum with stainless steel components