Bach 1¼G vs Bach 4GB
The Bach 1¼G has a wider cup diameter.
Mouthpiece A
Bach 1¼G
• Trombone
Cup diameter27.50 mm / 1.0827 in
Cup depthVery deep
Rim width—
Throat diameter7.01 mm / 0.2760 in
Backbore—
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 4GB
• Trombone
Cup diameter26.00 mm / 1.0236 in
Cup depthVery deep
Rim width—
Throat diameter7.01 mm / 0.2760 in
Backbore—
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Bach 1¼G has a cup diameter of 27.50 mm / 1.0827 in compared to 26.00 mm / 1.0236 in on the Bach 4GB — a difference of 1.50 mm / 0.0591 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 7.01 mm / 0.2760 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.