GR Technologies X66.8 C* vs Schilke 13A4a
The GR Technologies X66.8 C* has a wider cup diameter, the GR Technologies X66.8 C* features a deeper cup.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
GR Technologies X66.8 C*
• Trumpet
Cup diameter16.97 mm / 0.6681 in
Best suited for
Orchestral playing — large cup for full, dark tone
vs
Mouthpiece B
Schilke 13A4a
• Trumpet
Cup diameter16.76 mm / 0.6598 in
Cup Diameter
The GR Technologies X66.8 C* has a cup diameter of 16.97 mm / 0.6681 in compared to 16.76 mm / 0.6598 in on the Schilke 13A4a — a difference of 0.21 mm / 0.0083 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.