Bach 12 vs Bach 2½C
The Bach 2½C has a wider cup diameter, the Bach 12 features a deeper cup.
Mouthpiece A
Bach 12
• Cornet
Cup diameter15.20 mm / 0.5984 in
Cup depthVery deep
Rim width—
Throat diameter3.66 mm / 0.1441 in
Backbore—
Finish—
Material—
vs
Mouthpiece B
Bach 2½C
• Cornet
Cup diameter16.40 mm / 0.6457 in
Cup depthMedium
Rim width—
Throat diameter3.66 mm / 0.1441 in
Backbore—
Finish—
Material—
Best suited for
All-round versatile — balanced cup for general playing
Cup Diameter
The Bach 2½C has a cup diameter of 16.40 mm / 0.6457 in compared to 15.20 mm / 0.5984 in on the Bach 12 — a difference of 1.20 mm / 0.0472 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 12 has a very deep cup while the Bach 2½C has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
Throat diameters are essentially identical at 3.66 mm / 0.1441 in, so resistance feel will be comparable.
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.