I think most folks use either factory or other manufacturer's Ruger rings (like the Leupold posted above) to mount directly to the dovetailed rib already on the rifle. One exception might be the No. 1 heavy barreled varmint configuration with no rib - that takes separate bases where I typically see Weaver style bases used. If going a different route, a couple of other options have already been mentioned above (picatinny rail). One I don't think that has been mentioned is the Ruger to Weaver adapter that Burris makes allowing Burris or Weaver style rings to mount to the factory dovetailed rib.
