Kelly 3C vs Monette Cornet BP1-3D S5
The Kelly 3C has a wider cup diameter, the Kelly 3C features a deeper cup, the Kelly 3C has a larger throat opening.
Cup Diameter
The Kelly 3C has a cup diameter of 17.02 mm compared to 17.00 mm on the Monette Cornet BP1-3D S5 — a difference of +0.02 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Kelly 3C has a very deep cup while the Monette Cornet BP1-3D S5 has a deep cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Kelly 3C has a wider throat (4.06 mm vs 3.66 mm). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Kelly 3C is described as Lexan polycarbonate, and the Monette Cornet BP1-3D S5 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.