Kelly 31 vs Schilke 31B
The Kelly 31 has a wider cup diameter, the Kelly 31 features a deeper cup, the Kelly 31 has a larger throat opening.
Cup Diameter
The Kelly 31 has a cup diameter of 17.53 mm compared to 17.40 mm on the Schilke 31B — a difference of +0.13 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Kelly 31 has a — cup while the Schilke 31B has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Kelly 31 has a wider throat (3.80 mm vs 3.57 mm). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Kelly 31 is described as Lexan polycarbonate, and the Schilke 31B 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.