Bach 3B vs Bach 5B
The Bach 3B has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 3B
• Cornet
Cup diameter16.30 mm / 0.6417 in
vs
Mouthpiece B
Bach 5B
• Cornet
Cup diameter16.25 mm / 0.6398 in
Cup Diameter
The Bach 3B has a cup diameter of 16.30 mm / 0.6417 in compared to 16.25 mm / 0.6398 in on the Bach 5B — a difference of 0.05 mm / 0.0020 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.