This model is much like my Sub-Baritone Trumpet Mouthpiece, but a Trombone (or Euphonium) can actually sustain its sound.
It SHOULD fit perfectly onto MOST Trombones/Euphoniums.

Here's the Settings needed to print this decently (I have an Anycubic Kobra 3 3D Printer):

A bare minimum adhesive (hairspray)

20 mm Standard

No supports

0.4 Nozzle

Enjoy! :3