Which has a bigger cup — Kelly 12C or Yamaha SL-48L?

The Yamaha SL-48L has a cup diameter of 25.25 mm / 0.9941 in compared to 24.13 mm / 0.9500 in on the Kelly 12C — a difference of 1.12 mm / 0.0441 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Kelly 12C and Yamaha SL-48L?

The Yamaha SL-48L has a medium cup while the Kelly 12C has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

Kelly 12C vs Yamaha SL-48L

Name: Yamaha SL-48L
Brand: Yamaha

The Yamaha SL-48L has a wider cup diameter, the Yamaha SL-48L features a deeper cup.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material

Surface plating or treatment (e.g. silver plate, gold trim). Affects feel, durability, and appearance.

Mouthpiece A

Kelly 12C

• Trombone

Lead

Finish—

Best suited for

📋Lead trombone; smallest cup

Mouthpiece B

Yamaha SL-48L

• Trombone

Finish—

Best suited for

📣High-volume projection — open throat for power

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.