The roll pins are 1/16"roylt said:It is two roll pins. There is a drawing with part numbers in the back of your manual. I suggest you order new pins from Ruger. I did recycle mine but if you have an "oops" moment that would stink to have to wait for parts. I think Ruger sells them for 2 bucks for a set. When installing you will have to drill the new sight for fit. Go slow and be careful.
If memory serves it is a 3/16".
Good luck and Keep the P-guns alive!!