This is a marbles arms tang sight (aka Peep Sight) Winchester 1885 . It comes with 3 different sight apertures (1/2 inch diameter with .055 hole; 1/2 inch diameter with .102 hole; 3/4 inch diameter with .032 hole). Hole spacing on the base of the sight is 2.000 to 2.265 inches center to center, and the height adjustment is 1.680 inches to 2.015 inches, with a 18 degree angle. Mounting screws are NOT INCLUDED with the tang sight, so if you need those screws they can be purchased in the option box below.