Kelly 51D-EU vs Schilke 38D
The Kelly 51D-EU has a wider cup diameter, the Kelly 51D-EU features a deeper cup.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Kelly 51D-EU
• Baritone / Euphonium
ProfessionalCup diameter25.40 mm / 1.0000 in
Best suited for
Orchestral playing — large cup for full, dark tone
Professional euphonium
vs
Mouthpiece B
Schilke 38D
• Baritone / Euphonium
Cup diameter19.73 mm / 0.7768 in
Cup Diameter
The Kelly 51D-EU has a cup diameter of 25.40 mm / 1.0000 in compared to 19.73 mm / 0.7768 in on the Schilke 38D — a difference of 5.67 mm / 0.2232 in. A wider cup generally produces a fuller, darker tone but requires more air support.
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.