This is a used tritium rear sight by Trijicon made for select models of the STI Omni 1911 pistol. The trim inserts still glow as seen in pictures but you don't notice it unless it's really dark. There is no adjustments built into this, it is a solid chunk of metal. There is no dovetail, just the two screw holes to mount it which are .250" center to center, so could not be mounted on a standard 1911 pistol without some sort of adapter, or drilling and tapping for screws, or mounting this to a dovetail which you would slide in your pistol's existing slot. It is in excellent condition and shows no sign of damage.