Bach 1¼C vs Marcinkiewicz 303
The Marcinkiewicz 303 has a wider cup diameter, the Bach 1¼C features a deeper cup.
Cup Diameter
The Marcinkiewicz 303 has a cup diameter of 17.20 mm / 0.6772 in compared to 17.00 mm / 0.6693 in on the Bach 1¼C — a difference of 0.20 mm / 0.0079 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 1¼C has a medium cup while the Marcinkiewicz 303 has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
Throat diameters are essentially identical at 3.66 mm / 0.1441 in, so resistance feel will be comparable.
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.