Bach 1½GM vs Bach 1G
The Bach 1G has a wider cup diameter.
Mouthpiece A
Bach 1½GM
• Trombone
Cup diameter27.00 mm / 1.0630 in
Cup depthVery deep
Rim width—
Throat diameter8.10 mm / 0.3189 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 1G
• Trombone
Cup diameter28.00 mm / 1.1024 in
Cup depthVery deep
Rim width—
Throat diameter8.10 mm / 0.3189 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 1G has a cup diameter of 28.00 mm / 1.1024 in compared to 27.00 mm / 1.0630 in on the Bach 1½GM — a difference of 1.00 mm / 0.0394 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 8.10 mm / 0.3189 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.