Bach 17D vs Bruno Tilz 304- B 2
The Bach 17D has a wider cup diameter, the Bach 17D has a larger throat opening.
Cup Diameter
The Bach 17D has a cup diameter of 24.20 mm / 0.9528 in compared to 23.00 mm / 0.9055 in on the Bruno Tilz 304- B 2 — a difference of 1.20 mm / 0.0472 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Bach 17D has a wider throat (5.85 mm / 0.2303 in vs 4.60 mm / 0.1811 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.