Giardinelli 4M vs Kelly SKY-SS
The Giardinelli 4M has a wider cup diameter, the Giardinelli 4M features a deeper cup.
Cup Diameter
The Giardinelli 4M has a cup diameter of 25.40 mm / 1.0000 in compared to 24.64 mm / 0.9701 in on the Kelly SKY-SS — a difference of 0.76 mm / 0.0299 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Giardinelli 4M has a medium cup while the Kelly SKY-SS has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Giardinelli 4M is described as unspecified, and the Kelly SKY-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.