Giardinelli 4M vs Kelly BEAST-LS-SS

The Kelly BEAST-LS-SS has a wider cup diameter, the Kelly BEAST-LS-SS features a deeper cup.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material
Mouthpiece A
    Giardinelli 4M
    • Trombone
    Cup diameter25.40 mm / 1.0000 in
    Cup depthMedium
    Rim width
    Throat diameter6.40 mm / 0.2520 in
    Backbore1/4" (.250)
    Finish
    Material
    Best suited for
    📣High-volume projection — open throat for power
    vs
    Mouthpiece B
      Kelly BEAST-LS-SS
      • Trombone
      Bass
      Cup diameter28.70 mm / 1.1299 in
      Cup depth
      Rim width
      Throat diameter
      BackboreXL
      Finish
      Material316 Surgical Stainless Steel
      Best suited for
      🎻Orchestral playing — large cup for full, dark tone
      📋Extreme bass trombone; maximum breath support required

      Cup Diameter

      The Kelly BEAST-LS-SS has a cup diameter of 28.70 mm / 1.1299 in compared to 25.40 mm / 1.0000 in on the Giardinelli 4M — a difference of 3.30 mm / 0.1299 in. A wider cup generally produces a fuller, darker tone but requires more air support.

      Cup Depth

      The Kelly BEAST-LS-SS has a — cup while the Giardinelli 4M has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

      Material

      The Giardinelli 4M is described as unspecified, and the Kelly BEAST-LS-SS as 316 Surgical Stainless Steel. 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.

      Open in interactive tool + Add third mouthpiece Giardinelli 4M details Kelly BEAST-LS-SS details Giardinelli 4M equivalents Kelly BEAST-LS-SS equivalents