Kelly 7C-UK vs Marcinkiewicz 10
The Marcinkiewicz 10 has a wider cup diameter, the Marcinkiewicz 10 features a deeper cup, the Marcinkiewicz 10 has a larger throat opening.
Cup Diameter
The Marcinkiewicz 10 has a cup diameter of 16.84 mm / 0.6630 in compared to 16.51 mm / 0.6500 in on the Kelly 7C-UK — a difference of 0.33 mm / 0.0130 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Marcinkiewicz 10 has a deep cup while the Kelly 7C-UK has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Marcinkiewicz 10 has a wider throat (3.73 mm / 0.1469 in vs 3.66 mm / 0.1441 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Kelly 7C-UK is described as Lexan polycarbonate, and the Marcinkiewicz 10 as unspecified. 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.