Bach 1¼GM vs Bach 6½AL (large shank)
The Bach 1¼GM has a wider cup diameter, the Bach 1¼GM features a deeper cup, the Bach 1¼GM has a larger throat opening.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 1¼GM
• Trombone
Cup diameter27.50 mm / 1.0827 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
Cup diameter25.40 mm / 1.0000 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Bach 1¼GM has a cup diameter of 27.50 mm / 1.0827 in compared to 25.40 mm / 1.0000 in on the Bach 6½AL (large shank) — a difference of 2.10 mm / 0.0827 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.