I bought both RMSc and RMR adapter plates for the Ruger SP101. The RMSc plate fitted like a glove no filing needed to get it to fit.
The RMR plate required some filing on the sides to get the plate to squeeze in and some filing on the end in order to line up the anchor screw. But all easily done. Very much worth it to be able to use a red dot on the revolver. 5 stars.