Bob Reeves 43N/B/X vs Kelly 5C
The Bob Reeves 43N/B/X has a wider cup diameter.
Mouthpiece A
Bob Reeves 43N/B/X
• Cornet
Cup diameter17.07 mm / 0.6720 in
Cup depthVery deep
Rim width—
Throat diameter—
BackboreX
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
vs
Mouthpiece B
Kelly 5C
• Cornet
GeneralCup diameter16.76 mm / 0.6598 in
Cup depthVery deep
Rim width—
Throat diameter3.80 mm / 0.1496 in
BackboreM
Finish—
MaterialLexan polycarbonate
Best suited for
High-volume projection — open throat for power
Mid-range all-purpose
Cup Diameter
The Bob Reeves 43N/B/X has a cup diameter of 17.07 mm / 0.6720 in compared to 16.76 mm / 0.6598 in on the Kelly 5C — a difference of 0.31 mm / 0.0122 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a very deep cup depth, so the sound character from depth alone will be very similar.
Material
The Bob Reeves 43N/B/X is described as unspecified, and the Kelly 5C as Lexan polycarbonate. 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.