Kelly 18 vs Yamaha BB-BOBO-SOLO-GP
The Kelly 18 has a wider cup diameter, the Kelly 18 features a deeper cup.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Kelly 18
• Tuba
GeneralCup diameter32.77 mm / 1.2902 in
Best suited for
Orchestral playing — large cup for full, dark tone
Industry-standard tuba
vs
Mouthpiece B
Yamaha BB-BOBO-SOLO-GP
• Tuba
Cup diameter32.20 mm / 1.2677 in
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Kelly 18 has a cup diameter of 32.77 mm / 1.2902 in compared to 32.20 mm / 1.2677 in on the Yamaha BB-BOBO-SOLO-GP — a difference of 0.57 mm / 0.0224 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.