This vintage production peep sight is steel unlike current production. Includes two eye disks, easily installed on Thompson Center, Lyman Deerstalker, Lyman Trade Rifle, and similar Hawken rifles. Two mounting screws included. Features 1/4 minute micrometer click adjustments for elevation and windage, quick release slide. Small 5/8" diameter knurled disk is drilled .040". Large 1/2" diameter knurled disk is drilled with a .092" aperture for large field of view and quick target acquisition. Made in the U.S.A. by Lyman, this sight is a favorite of target shooters. It may require drilling and tapping an 8-32 hole. This sight has the original factory cardboard box with the flap torn.