If you use the Ruger 30mm rings . . . the inside distance between them is only 1 7/8", so whatever tube red dot you get . . . The control group will need to be less than 1 7/8" long. The other option is to get the weaver mount unit that fits in your milled in ruger scope mounts. I just put a 30mm red dot on on my SRH. It took some looking to find a red dot tube with the right sized control group . . . but I like the Ruger rings better than the weaver system for strength and durability. I also have a 1" 2x6 scope, and it's easy to switch back and forth between the two, and I didn't have to remove my rear fixed sight, so if anything goes wrong . . . it only takes a couple of seconds to remove the red dot or scope and use the fixed sights.