Bach 5GS (large shank) vs Bach 6½AL (large shank)
The Bach 5GS (large shank) has a wider cup diameter.
The narrowest point at the bottom of the cup. Affects resistance, volume, and tone color.
Mouthpiece A
Bach 5GS (large shank)
• Trombone
Throat diameter6.63 mm / 0.2610 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 6½AL (large shank)
• Trombone
Throat diameter6.63 mm / 0.2610 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Throat Diameter
Throat diameters are essentially identical at 6.63 mm / 0.2610 in, so resistance feel will be comparable.
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.