Bach 1½C vs Kelly 7C
The Bach 1½C has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 1½C
• Cornet
Cup diameter17.00 mm / 0.6693 in
vs
Mouthpiece B
Kelly 7C
• Cornet
GeneralCup diameter16.51 mm / 0.6500 in
Best suited for
All-round versatile — balanced cup for general playing
Beginner / intermediate
Cup Diameter
The Bach 1½C has a cup diameter of 17.00 mm / 0.6693 in compared to 16.51 mm / 0.6500 in on the Kelly 7C — a difference of 0.49 mm / 0.0193 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.