Green Blob Outdoors (Black) Tactical Iron Flip up Front & Rear Sights, Rail Mount Gas Block 223, 5.56. High quality flip-up front and rear sight towers complete with A2 square post assembly with locking retention and precision elevation adjustments for greater accuracy. Mounting Decks designed to be used with handguard rails or front gas blocks (front sight tower) and both will fit all 7/8 Thumbnuts With Locking Retention For Maintaning Zero Under Heavy Conditions Easy And Quick Installation, aircraft aluminum construction with black matte finish 6061-T6 Aluminum Alloy, For mounting on same plane