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Bach 15D vs Bach 18D

The Bach 15D has a wider cup diameter.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
    Bach 15D
    • Trombone
    Cup diameter24.40 mm / 0.9606 in
    Best suited for
    📣High-volume projection — open throat for power
    vs
    Mouthpiece B
      Bach 18D
      • Trombone
      Cup diameter24.20 mm / 0.9528 in
      Best suited for
      📣High-volume projection — open throat for power

      Cup Diameter

      The Bach 15D has a cup diameter of 24.40 mm / 0.9606 in compared to 24.20 mm / 0.9528 in on the Bach 18D — a difference of 0.20 mm / 0.0079 in. A wider cup generally produces a fuller, darker tone but requires more air support.

      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.

      Open in interactive tool + Add third mouthpiece Bach 15D details Bach 18D details Bach 15D equivalents Bach 18D equivalents

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