Bach 6½AL (large shank) vs Kelly 12C
The Bach 6½AL (large shank) has a wider cup diameter, the Bach 6½AL (large shank) features a deeper cup.
The width of the rim surface that contacts the lips. Wider rims improve endurance; narrower rims improve flexibility.
Mouthpiece A
Bach 6½AL (large shank)
• Trombone
Rim width—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Kelly 12C
• Trombone
LeadRim width—
Best suited for
Lead trombone; smallest cup
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.