Bach 18 vs Schilke 43A
The Bach 18 has a wider cup diameter, the Schilke 43A has a larger throat opening.
How deep the cup is, from shallow (brighter, easier high register) to deep (darker, fuller sound).
Mouthpiece A
Bach 18
• Trombone
Cup depthMedium
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Schilke 43A
• Trombone
Cup depthMedium
Best suited for
High-volume projection — open throat for power
Cup Depth
Both mouthpieces share a medium cup depth, so the sound character from depth alone will be very similar.
Which is better?
Neither mouthpiece clearly dominates the other — the right choice depends on your embouchure, playing style, and the sound you're after. Try both if possible.