Bob Reeves RP5 vs GR Technologies 65SZ
The GR Technologies 65SZ has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bob Reeves RP5
• Trumpet
Cup diameter16.47 mm / 0.6484 in
vs
Mouthpiece B
GR Technologies 65SZ
• Trumpet
Cup diameter16.50 mm / 0.6496 in
Cup Diameter
The GR Technologies 65SZ has a cup diameter of 16.50 mm / 0.6496 in compared to 16.47 mm / 0.6484 in on the Bob Reeves RP5 — a difference of 0.03 mm / 0.0012 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.