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 harms way. In service of this mission, Strike brings to you, the new SI Strike Rail. Lightweight, high strength, everything you need, and nothing you dont. Features : "1.57" internal Diameter for suppressor or Oppressor compatibility, For AR-15 style rifles only. Not compatible with AR-10 receivers. MLOK compatible Ambidextrous QD socket placement Built in anti rotation feature in rail Aluminum barrel nut