MicroShift Mezzo rear derailleur pulleys (8 speed, 12 teeth)

Disclaimer: I don't use this derailleur and just took the measurements of the new pulleys in case I ever need them in the future. I use almost the same 3D-printed pulleys for Shimano Deore, they ran more than 5000 km without any issues already.

Differences from the original pulleys:
1) The bearing hole diameter tolerance for the tension pulley was set to +0.2mm, for the guide pulley to +0.05mm, as tested using Ender3V2 with PETG.
2) Useless holes were removed to increase the strength and reliability.
3) All the height dimensions were optimized for 0.12mm layer height.

Print settings:
Plastic: PETG or better (not PLA!).
Layer height: 0.12 mm.
Nozzle: 0.4 mm.
Speed: 30 mm/s.
Infill: 100%.

The reliability of the parts very much depend on these settings and on the plastic quality.

Print both sides and glue them together with any cyanoacrylate glue. Clean the seam inside the bearing holes using a round file or a dremel if needed. Metal parts are taken from the original worn-out pulleys.

The guide and the tension pulleys are almost the same, but the tension pulley has little chamfers on one sides of the teeth. Make sure you install it so that these chamfers look towards the oncoming chain. 

I recommend to have a pair of backup original pulleys if you ride on long distances. I hope you understand that I give no warranty on the stuff that you print :) It may break at once or work for thousands of kilometers, you never know until you try...

If you print it, upload your photos, because I didn't make mine.