I have a Umarex Trevox airgun for which the rear sight broke. The original sight is pretty fragile (and so is the 3D printed replacement)! I reverse engineered what was left of the original, and tweaked it somewhat for printing.
I printed in Prusament PETG using a 0.25mm nozzle on my MK4. The new sight works well, although I have not found replacements for the Tritium (maybe a knockoff) inserts.
The author marked this model as their own original creation.