My earliest pet project while I was at Battle Arms had come home :)
The Matech backup rear sight was one of the first backup sights to feature an adjustable elevation, more information can be found on Matech's site http://www.matech.net/smallarms/iron-sights
Well made and tough, it can be found on many issued M16s and civilian owned AR15s.
But it isn't without its share of shortcomings, chief among them is the mounting bracket and recoil screw, which the Retrofit Kit, Matech (RKM) aims to address.
RKM (retrofit kit, Matech) has a redesigned and reinforced clamp (machined from 1080 carbon bar stock steel, manganese phosphate plated), and a grade 8 screw (same grade as the carrier gas key screws). RKM's grade 8 screw has a smaller diameter Allen socket, and is far more appropriate for the diameter of the screw and there is less chance of over torquing. The clamp is significantly thicker, and redesigned in 2016 for a less snag prone profile.
RKM's grade 8 screw requires a 7/64 size Allen wrench, and is not included.
Made in the US.