Kelly 51D-EU-SS vs Schilke 38D
The Kelly 51D-EU-SS has a wider cup diameter, the Kelly 51D-EU-SS features a deeper cup.
Cup Diameter
The Kelly 51D-EU-SS has a cup diameter of 25.40 mm / 1.0000 in compared to 19.73 mm / 0.7768 in on the Schilke 38D — a difference of 5.67 mm / 0.2232 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 Schilke 38D has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Kelly 51D-EU-SS is described as 316 Surgical Stainless Steel, and the Schilke 38D 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.