Bob Reeves RP4 vs GR Technologies 64Z**
Both mouthpieces share similar core dimensions — the differences are in the details.
Mouthpiece A
Bob Reeves RP4
• Trumpet
Cup diameter16.27 mm / 0.6406 in
Cup depthShallow
Rim width—
Throat diameter—
Backbore—
Finish—
Material—
vs
Mouthpiece B
GR Technologies 64Z**
• Trumpet
Cup diameter16.26 mm / 0.6402 in
Cup depthShallow
Rim width—
Throat diameter—
Backbore—
Finish—
Material—
Cup Diameter
Both mouthpieces have virtually identical cup diameters at 16.27 mm / 0.6406 in.
Cup Depth
Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.
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.