Bach 18 vs Schilke 43A
The Bach 18 has a wider cup diameter, the Schilke 43A has a larger throat opening.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 18
• Trombone
Cup diameter24.20 mm / 0.9528 in
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Schilke 43A
• Trombone
Cup diameter23.57 mm / 0.9280 in
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Bach 18 has a cup diameter of 24.20 mm / 0.9528 in compared to 23.57 mm / 0.9280 in on the Schilke 43A — a difference of 0.63 mm / 0.0248 in. A wider cup generally produces a fuller, darker tone but requires more air support.
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.