Bach 3G vs Bach 4GB
The Bach 3G has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 3G
• Trombone
Cup diameter26.26 mm / 1.0339 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 4GB
• Trombone
Cup diameter26.00 mm / 1.0236 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Bach 3G has a cup diameter of 26.26 mm / 1.0339 in compared to 26.00 mm / 1.0236 in on the Bach 4GB — a difference of 0.26 mm / 0.0102 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.