Schilke 13A4a vs Schilke 18C3d
The Schilke 18C3d has a wider cup diameter, the Schilke 18C3d features a deeper cup, the Schilke 13A4a has a larger throat opening.
Cup Diameter
The Schilke 18C3d has a cup diameter of 17.52 mm / 0.6898 in compared to 16.76 mm / 0.6598 in on the Schilke 13A4a — 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 Schilke 18C3d has a medium cup while the Schilke 13A4a has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Schilke 13A4a has a wider throat (3.66 mm / 0.1441 in vs 3.65 mm / 0.1437 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
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.