Versitile mount at a great price - Ruger Mark III, Mark IV & 22/45 Picatinny Mount, w/ Pre-Drilled Recievers

This mount is unique in that it can be mounted in two ways. One way it allows you to mount it just in front of the the rear sight without having to remove it. This way the rail overhangs the barrel by about an inch. The rail is low enough that you can see/use your sights over the rail. The second option is to mount it flipped around. I this position the mount is flush with the front of the receiver and it extends back over where the (removed) rear sight was. By removing the rear (and front) sight, it gives you a clean looking install. Note the mount is relieved on both sides to coincide with the ejection port as mounted.
Lastly, it is not hard to trim the rail ( with a hack saw) so that it mounts between the rear sight and front of the receiver for a compact look.

Screws are included and are even treated with thread lock.