My son needed a cup mute for jazz band, and it seemed like a fun quick project and this is the result. it prints in two pieces with no support, and may require a little sanding where the parts mate to get them to fit smoothly. I printed it at .35 for speed and that made the tolerances tighter. At .2 it will likely slide on smoother (maybe too smooth). once printed we cut up some cork from wine bottles and glued them on. if you take the cup out it works as a straight mute as well. His jazz is now muted.
I used PETG since it will likely have to travel in hot vehicles, if you do try this at .20, please let me know your results and I'll update this, and possible adjust the tolerances with a second file.