Schilke 51B vs Yamaha SL-48S-GP
The Schilke 51B has a wider cup diameter, the Yamaha SL-48S-GP has a larger throat opening.
Cup Diameter
The Schilke 51B has a cup diameter of 25.63 mm / 1.0091 in compared to 25.25 mm / 0.9941 in on the Yamaha SL-48S-GP — a difference of 0.38 mm / 0.0150 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a medium cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Yamaha SL-48S-GP has a wider throat (6.62 mm / 0.2606 in vs 6.53 mm / 0.2571 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
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.