Bach 9D vs Kelly SCREAMER-UK
The Bach 9D has a wider cup diameter, the Bach 9D has a larger throat opening.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 9D
• Cornet
Cup diameter16.05 mm / 0.6319 in
Best suited for
Lead / commercial — shallow cup for brightness and range
vs
Mouthpiece B
Kelly SCREAMER-UK
• Cornet
LeadCup diameter16.00 mm / 0.6299 in
Best suited for
Lead / commercial — shallow cup for brightness and range
Screamer / high notes — tight throat with shallow cup
Lead / soprano cornet
Cup Diameter
The Bach 9D has a cup diameter of 16.05 mm / 0.6319 in compared to 16.00 mm / 0.6299 in on the Kelly SCREAMER-UK — 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.