Bach 15 vs Kelly 5G-EU
The Kelly 5G-EU has a wider cup diameter, the Kelly 5G-EU features a deeper cup.
Cup Diameter
The Kelly 5G-EU has a cup diameter of 25.40 mm / 1.0000 in compared to 24.40 mm / 0.9606 in on the Bach 15 — 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
The Kelly 5G-EU has a — cup while the Bach 15 has a deep cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Bach 15 is described as unspecified, and the Kelly 5G-EU as Lexan polycarbonate. Material affects mass, warmth, and how quickly the piece responds.
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.