Kelly MC vs Marcinkiewicz 17
The Marcinkiewicz 17 has a wider cup diameter, the Marcinkiewicz 17 has a larger throat opening.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Kelly MC
• French Horn
GeneralCup diameter16.76 mm / 0.6598 in
Best suited for
High-volume projection — open throat for power
All-purpose French horn
vs
Mouthpiece B
Marcinkiewicz 17
• French Horn
Cup diameter17.42 mm / 0.6858 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Marcinkiewicz 17 has a cup diameter of 17.42 mm / 0.6858 in compared to 16.76 mm / 0.6598 in on the Kelly MC — a difference of 0.66 mm / 0.0260 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.