Bach 1½C vs Kelly 5C
The Bach 1½C has a wider cup diameter, the Kelly 5C features a deeper cup, the Kelly 5C has a larger throat opening.
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 5C
• Cornet
GeneralCup diameter16.76 mm / 0.6598 in
Best suited for
High-volume projection — open throat for power
Mid-range all-purpose
Cup Diameter
The Bach 1½C has a cup diameter of 17.00 mm / 0.6693 in compared to 16.76 mm / 0.6598 in on the Kelly 5C — a difference of 0.24 mm / 0.0094 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.