Conn Imp. Precision 4 vs Kelly 5C
The Kelly 5C has a wider cup diameter, the Kelly 5C features a deeper cup.
The taper behind the throat leading to the shank. Affects projection and tone character.
Mouthpiece A
Conn Imp. Precision 4
• Cornet
GeneralBackbore—
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
GeneralBackboreM
Best suited for
High-volume projection — open throat for power
Mid-range all-purpose
Which is better?
Both mouthpieces are categorized as "General" — the physical dimensions above will determine which suits your embouchure and playing style better.