I lap Leupold Rings and Ruger rings. Ruger rings IMHO are some of the worst aligned rings made and have to be lapped. I have not had a single scope using Ruger Rings on a Number 1 or 77 that did not get scope marks on it not a one. They are easy to lap though and no problems after that procedure. I usually lap 75% of the surface more or less before I place the scope in the rings. I also cold blue the inside surfaces that were lapped especially Leupolds otherwise they will rust.