You merely have to mill the sides of the rib for Ruger rings and mill recess in top of rib for recoil lug on bottom of Ruger ring. Rib is perfectly nice in appearance and it works perfectly. I have done it on one quarter rib on a 375 I didn't wish to alter the bolt handle to low scope so adapted to scout scope. I also replaced the blocks in the Chapuis double I had with sections cut from a Ruger rib for the same effect but allowing return to original configuration. Should be much cheaper than ANY mount such as an ERA.