Bach 5GB (large shank) vs Bach 6½A (large shank)
The Bach 5GB (large shank) has a wider cup diameter, the Bach 5GB (large shank) features a deeper cup.
The taper behind the throat leading to the shank. Affects projection and tone character.
Mouthpiece A
Bach 5GB (large shank)
• Trombone
Backbore—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 6½A (large shank)
• Trombone
Backbore—
Best suited for
Orchestral playing — large cup for full, dark tone
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.