Bob Reeves 4G/JF vs Kelly 6-1/2AL-SS

The Bob Reeves 4G/JF has a wider cup diameter, the Kelly 6-1/2AL-SS features a deeper cup.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material
Mouthpiece A
    Bob Reeves 4G/JF
    • Trombone
    Cup diameter26.00 mm
    Cup depthDeep
    Rim width
    Throat diameter
    Backbore
    Finish
    Material
    Best suited for
    🎻Orchestral playing — large cup for full, dark tone
    vs
    Mouthpiece B
      Kelly 6-1/2AL-SS
      • Trombone
      General
      Cup diameter25.15 mm
      Cup depthVery deep
      Rim width
      Throat diameter
      BackboreM
      Finish
      Material316 Surgical Stainless Steel
      Best suited for
      🎻Orchestral playing — large cup for full, dark tone
      📋Standard trombone / baritone

      Cup Diameter

      The Bob Reeves 4G/JF has a cup diameter of 26.00 mm compared to 25.15 mm on the Kelly 6-1/2AL-SS — a difference of +0.85 mm. A wider cup generally produces a fuller, darker tone but requires more air support.

      Cup Depth

      The Kelly 6-1/2AL-SS has a very deep cup while the Bob Reeves 4G/JF has a deep cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

      Material

      The Bob Reeves 4G/JF is described as unspecified, and the Kelly 6-1/2AL-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 Bob Reeves 4G/JF details Kelly 6-1/2AL-SS details Bob Reeves 4G/JF equivalents Kelly 6-1/2AL-SS equivalents