Bach 11½A vs Bach 18
The Bach 11½A has a wider cup diameter.
Mouthpiece A
Bach 11½A
• Cornet
Cup diameter15.65 mm / 0.6161 in
Cup depthVery deep
Rim width—
Throat diameter3.66 mm / 0.1441 in
Backbore—
Finish—
Material—
vs
Mouthpiece B
Bach 18
• Cornet
Cup diameter15.10 mm / 0.5945 in
Cup depthVery deep
Rim width—
Throat diameter3.66 mm / 0.1441 in
Backbore—
Finish—
Material—
Cup Diameter
The Bach 11½A has a cup diameter of 15.65 mm / 0.6161 in compared to 15.10 mm / 0.5945 in on the Bach 18 — a difference of 0.55 mm / 0.0217 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a very deep cup depth, so the sound character from depth alone will be very similar.
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.