Strike Industries Strike Rail M-LOK Handguard, Fits AR15, 13.5, Anodized Finish, Black SI-StrikeRail-135-BK The SI Strike Rail for the AR-15 was developed to fulfill the requirements of certain agency partners" who wanted a lightweight" but feature packed rail that they could depend on when entering harm's way. In service of this mission" Strike brings to you" the new SI Strike Rail. Lightweight" high strength" everything you need" and nothing you don't.