Long-range engagements can quickly move to close quarters and optical sights can fail or get damaged in combat situations. To give shooters and tactical operators an instant, dependable back-up sight system, Brownells proudly announces its flip-up sights for flattop AR-15/M16 rifles and carbines. Both front and rear sights' feature a detent ball locking system for ease of use and reliable sight repeatability and clamp to either Picatinny or Weaver rails with stout, 1/2-inch nuts. The rear sight clamps directly to a flattop rail and features a .108 inch diameter aperture that provides excellent field of view for both short- and long-range targets. Deep grooves in the sight's sides ensure a positive grip for rapid deployment. Brownells folding front sight attaches to a rifle's rail gas block. Thick, protective ears prevent damage to the sight post during the most demanding conditions and it uses the proven, square, elevation-adjustable AR-15/M16 sight post.