Bach 8½A vs Kelly 3C
The Kelly 3C has a wider cup diameter, the Kelly 3C has a larger throat opening.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 8½A
• Cornet
Cup diameter16.10 mm / 0.6339 in
vs
Mouthpiece B
Kelly 3C
• Cornet
GeneralCup diameter17.02 mm / 0.6701 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
All-purpose mid-range
Cup Diameter
The Kelly 3C has a cup diameter of 17.02 mm / 0.6701 in compared to 16.10 mm / 0.6339 in on the Bach 8½A — a difference of 0.92 mm / 0.0362 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.