Bach 5A vs Bach 8½A
The Bach 5A has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 5A
• Cornet
Cup diameter16.25 mm / 0.6398 in
vs
Mouthpiece B
Bach 8½A
• Cornet
Cup diameter16.10 mm / 0.6339 in
Cup Diameter
The Bach 5A has a cup diameter of 16.25 mm / 0.6398 in compared to 16.10 mm / 0.6339 in on the Bach 8½A — a difference of 0.15 mm / 0.0059 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.