Denis Wick 3 vs Kelly 3C
The Kelly 3C has a wider cup diameter, the Denis Wick 3 has a larger throat opening.
Cup Diameter
The Kelly 3C has a cup diameter of 17.02 mm / 0.6701 in compared to 16.75 mm / 0.6594 in on the Denis Wick 3 — a difference of 0.27 mm / 0.0106 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a very deep cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Denis Wick 3 has a wider throat (4.57 mm / 0.1799 in vs 4.06 mm / 0.1598 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Denis Wick 3 is described as unspecified, and the Kelly 3C 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.