Conn Imp. Precision 4 vs Kelly 5C
The Kelly 5C has a wider cup diameter, the Kelly 5C features a deeper cup.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Conn Imp. Precision 4
• Cornet
GeneralCup diameter16.41 mm / 0.6461 in
Best suited for
All-round versatile — balanced cup for general playing
Players with large full lips; most common surviving example
Bright tone; same as Model 3 with wide rim
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 Kelly 5C has a cup diameter of 16.76 mm / 0.6598 in compared to 16.41 mm / 0.6461 in on the Conn Imp. Precision 4 — a difference of 0.35 mm / 0.0138 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.