Bach 4G vs Bach 5G (large shank)
The Bach 4G has a wider cup diameter.
Mouthpiece A
Bach 4G
• 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
vs
Mouthpiece B
Bach 5G (large shank)
• Trombone
Cup diameter25.50 mm / 1.0039 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 4G has a cup diameter of 26.00 mm / 1.0236 in compared to 25.50 mm / 1.0039 in on the Bach 5G (large shank) — a difference of 0.50 mm / 0.0197 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.