Bach 18 vs Marcinkiewicz CH EF 21J. Cox
The Marcinkiewicz CH EF 21J. Cox has a wider cup diameter, the Marcinkiewicz CH EF 21J. Cox features a deeper cup, the Marcinkiewicz CH EF 21J. Cox has a larger throat opening.
Cup Diameter
The Marcinkiewicz CH EF 21J. Cox has a cup diameter of 17.48 mm / 0.6882 in compared to 16.15 mm / 0.6358 in on the Bach 18 — a difference of 1.33 mm / 0.0524 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Marcinkiewicz CH EF 21J. Cox has a very deep cup while the Bach 18 has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Marcinkiewicz CH EF 21J. Cox has a wider throat (4.57 mm / 0.1799 in vs 4.50 mm / 0.1772 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.