Update: Added Version 3. It has even better printability. Update: Be sure to try Version 2. There are some slight shape changes that improve printability and smooth use. The SCAD file has more documentation and more configuration options. The V2 STL files reflect these changes. I also have found that NinjaFlex Semiflex is the best filament for this object of the filaments that I have tested. Taulman Bridge is a close second.Though the little Tourte mutes are dirt cheap, I missed the old Yehudi Menuhin "flip-top" mutes because you could put them on and take them off really fast. Since they don't make them anymore, I figured I'd design something along similar lines, but with good printability and modability.Since I am a Violist, the dimensions were first tuned for a Viola. If you need a mute for a Violin or Cello, simply load the included OpenSCAD file, change a few named parameters, and generate a new STL file, or try the STL files. The OpenSCAD parameters are documented in the file.I first printed it in Flex EcoPLA, but it was way too floppy. I then printed it in Taulman Bridge, and I am happy with the degree of firmness and give. I don't think that ABS or PLA will work as well, since they might be so stiff as to dent the bridge. My settings with Taulman Bridge were:Layer Height: 0.2mmShell Thickness (and Top/Bottom): 0.8mmFill Density: 20%Print Speed: 30mm/sPrint Temp: 242CNo FanI printed on an Ultimaker Original. My HBK has not arrived, so I printed on cold glass coated with diluted elmers glue.Assemble by snapping the cones in the mute base into the hollows in the mute arm. You can bend the base to do so. Put it on your instrument by hooking your lower middle string (Viola/Cello:G, Violin:D) with the base then pulling the base over a bit to hook the upper middle string (Viola/Cello:D, Violin:A). Slide the base to the position between the bridge and the tail that allows the mute pincers to grip the bridge when the arm is swung into place.I am finding that this works best with the base connected to the inner strings, but you can set the str_dist variable to a larger number if you want to grip the outer strings.Edit: I uploaded revised files, including a cello mute and better documentation of the OpenSCAD parameters.