This super heavy duty rear sight is removable and based upon the classic A2 sight, but will work with "F" height front sight posts and red dot optics to be co-witnessed. The sight is adjustable for windage and elevation. The LMT sight was first used in 2001 on the Mk18 Mod 0, which started as a shipboard weapon. The Rock River sight resembles the LMT.
Rock River is an old school manufacturer. Part of the original hard core Mil-Spec manufacturers like Colt, LMT, Bushmaster, CMMG, and the like. They make no-BS parts. The RRA rear A2 sight is removable and solid 6061 forged aluminum. RRA also is a major name in National Match competitions.