Conn Precision 3 vs Kelly 3C
The Kelly 3C has a wider cup diameter, the Kelly 3C features a deeper cup.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Conn Precision 3
• Cornet
GeneralCup diameter16.41 mm / 0.6461 in
Best suited for
All-round versatile — balanced cup for general playing
All-around use; most popular model
Bright quality of tone in all registers; good all-around
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 16.41 mm / 0.6461 in on the Conn Precision 3 — a difference of 0.61 mm / 0.0240 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Which is better?
Both mouthpieces are categorized as "General" — the physical dimensions above will determine which suits your embouchure and playing style better.