Denis Wick RW4B vs Kelly 7C-UK
The Kelly 7C-UK has a wider cup diameter, the Denis Wick RW4B has a larger throat opening.
Cup Diameter
The Kelly 7C-UK has a cup diameter of 16.51 mm / 0.6500 in compared to 16.50 mm / 0.6496 in on the Denis Wick RW4B — a difference of 0.01 mm / 0.0004 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a medium cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Denis Wick RW4B has a wider throat (4.27 mm / 0.1681 in vs 3.66 mm / 0.1441 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Denis Wick RW4B is described as unspecified, and the Kelly 7C-UK 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.