Bach 10½A vs Bach 18
The Bach 10½A has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 10½A
• Cornet
Cup diameter15.90 mm / 0.6260 in
vs
Mouthpiece B
Bach 18
• Cornet
Cup diameter15.10 mm / 0.5945 in
Cup Diameter
The Bach 10½A has a cup diameter of 15.90 mm / 0.6260 in compared to 15.10 mm / 0.5945 in on the Bach 18 — a difference of 0.80 mm / 0.0315 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.