Works on ruger mark iii hunter, but it's tight - JP Enterprises JPoint Mount Adapters for Pistols

I bought this to mount the JPoint circle-dot reflex sight on my Mark III. It does fit - it's not just for the Mark II. Not sure it would fit on the 22/45. You remove the rear sight and slide this one into place.

Be advised, this fits very tight, on mine anyway. I had a gunsmith install it. He filed on it a bit but it is hard anodized aluminum. He then used an aluminum drift to bang it in. He said using anything else (brass, steel) would mar it. He got it centered nicely because zeroing only required a fraction of a turn on the adjustment screws. If you remove the receiver/barrel assembly from the frame to do this, put a piece of tape over the pin that holds the loaded chamber indicator in. That pin falls out easily.

This makes for a nice, clean, low-profile mount of the JPoint sights on these Rugers. Might work on other guns with the same dovetail but it would be a gamble.