Giardinelli 4M vs Kelly 51D-EU
the Kelly 51D-EU features a deeper cup.
Mouthpiece A
Giardinelli 4M
• Baritone / Euphonium
Cup diameter25.40 mm / 1.0000 in
Cup depthMedium
Rim width—
Throat diameter6.40 mm / 0.2520 in
Backbore1/4" (.250)
Finish—
Material—
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Kelly 51D-EU
• Baritone / Euphonium
ProfessionalCup diameter25.40 mm / 1.0000 in
Cup depth
Rim width—
Throat diameter—
BackboreL
Finish—
MaterialLexan polycarbonate
Best suited for
Orchestral playing — large cup for full, dark tone
Professional euphonium
Cup Diameter
Both mouthpieces have virtually identical cup diameters at 25.40 mm / 1.0000 in.
Cup Depth
The Kelly 51D-EU has a — cup while the Giardinelli 4M has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Giardinelli 4M is described as unspecified, and the Kelly 51D-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.