Bach 1½C vs Conn Precision 1
The Bach 1½C has a wider cup diameter, the Conn Precision 1 features a deeper cup.
Cup Diameter
The Bach 1½C has a cup diameter of 17.00 mm / 0.6693 in compared to 16.56 mm / 0.6520 in on the Conn Precision 1 — a difference of 0.44 mm / 0.0173 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Conn Precision 1 has a — cup while the Bach 1½C has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Bach 1½C is described as unspecified, and the Conn Precision 1 as Silver-plated brass. 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.