I went to
https://apps.kubotausa.com/illustrated-parts/ and after agreeing to the legal, put in your
MMM model RC60-21B.
Everything came back to B2150.
If you go there and search your
tractor's model (there's 4 or 5 versions of B7100), hit "Local Options" and it will show compatible implement models of all types; MMM's, snowblowers, backhoes, etc.
Looks like most MMM's are versions of -62H, -71H or -71B. The trick is to get the required mounting hardware to attach it....