The Lyman 17A Insert set includes two post inserts, five aperture inserts and one bead insert. Blued steel. 3/8" dovetail. Height is from bottom of dovetail to center of aperture. Kit Includes:Two post-type inserts (.050 and .100 wide) One bead insert Five aperture-type inserts (One plastic with a .120 hole and 4 steel inserts with .093, .102, .110 and .120 holes)