It's ridiculously loose -- the standard nylon Scrap Yard S6 sheath isn't horrible in length for a RMD, or even in thickness, but there's way too much difference in the blade height. I measured an S6 and a RMD -- the RMD's height is 1 7/16-inch, and the S6 is 1 5/8, so that doesn't seem too bad. However, the S6 sheaths are sized to accommodate not merely the cutting edge height, but the height behind the choil (without binding) -- that's 1 7/8-inch, so a nylon S6 sheath has almost 1/2-inch of side-to-side slack for a RMD.