Bach 5GB (large shank) vs Bach 6½A (large shank)
The Bach 5GB (large shank) has a wider cup diameter, the Bach 5GB (large shank) features a deeper cup.
Cup Diameter
The Bach 5GB (large shank) has a cup diameter of 25.50 mm / 1.0039 in compared to 25.40 mm / 1.0000 in on the Bach 6½A (large shank) — a difference of 0.10 mm / 0.0039 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 5GB (large shank) has a very deep cup while the Bach 6½A (large shank) has a deep 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 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.
Compare Bach 5GB (large shank) with others
Compare Bach 6½A (large shank) with others
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