Denis Wick SM4 vs Kelly 51D-EU-SS
The Denis Wick SM4 has a wider cup diameter, the Kelly 51D-EU-SS features a deeper cup.
Cup Diameter
The Denis Wick SM4 has a cup diameter of 26.00 mm / 1.0236 in compared to 25.40 mm / 1.0000 in on the Kelly 51D-EU-SS — a difference of 0.60 mm / 0.0236 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Kelly 51D-EU-SS has a — cup while the Denis Wick SM4 has a very deep cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Denis Wick SM4 is described as unspecified, and the Kelly 51D-EU-SS as 316 Surgical Stainless Steel. 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.