This Williams Gun Sight Company manufactured WGRS series open sight blade green fiber optic receiver sight with both mounting screws is for the Ruger model 10/22 semi-auto rimfire rifle in 22 LR caliber and is in as new condition. The receiver 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