The first R-Adapter M I bought for the M-P was so tight on the R-mount flange I thought it would break something, so I returned it. The second one arrived yesterday—this one's a perfect fit on both flanges. I'm sure the variation is just fractional hundredths of a mm ..

It's a nice mount adapter, with its removable tripod mount and 6-bit EXIF data trigger. Just a little more than the Rayqual Nikon F to M-mount adapter too (less than the Novoflex).