This is the rear sight base that fits the ORIGINAL rear sight on the Winchester 1890 and 1906. This little screw sits in the rear dovetail on the barrel and holds the rear sight in place. Slide this part into the dovetail and set the rear sight on top of the screw. Turn clockwise and it will thread into the rear sight pulling it tight against the barrel. (the sight is not included, it is just there for reference)
