Nice fit and finish - TANDEMKROSS Shadow Picatinny Rail, Ruger MKII/III/IV and 22/45

This is pretty much how Ruger should have designed the rail for the Mark series pistols. You can sight through the groove down the center when optics are not installed, it is a little on the tall side though, so you might want to change to a more direct-mount plate once you decide what optic you are going to use (I can't fault the design for that).