This Williams Gun Sight Company manufactured WGRS series receiver peep sight with Twilight aperture, both mounting screws and a .570" high front sight with a 1/16" gold bead is for the Ruger model 10/22 semi-auto rimfire rifle in 22 LR caliber and is in as new condition. The receiver peep sight mounts on the top rear section of the receiver where your scope mounting base would normally attach.  (file photo)

Note: This is a CFnParts exclusive non-catalogued Williams Gun Sight Company manufactured receiver sight.