Theo Wanne Glass gauges are used with Theo Wanne Feeler Gauges to measure mouthpiece facings and are available in both traditional and metric. How to Measure a Mouthpiece Facing:
1. Place the glass plate (gauge) on the table of the mouthpiece such that it extends over the facing curve much like a reed would.
2. Align the ‘0’ line of the glass gauge with the tip of the mouthpiece.
3. Place a feeler gauge between the glass and the facing of the mouthpiece.
4. Slide the feeler gauge back until it is snug between the glass and mouthpiece facing.
5. Record the distance marked on the glass gauge, and the feeler gauge size used. Example: The mouthpiece shown in the picture has a facing 18mm back from the tip with a.25mm feeler gauge.
6. Repeat with each feeler gauge.
7. You can now plot the facing curve of your mouthpiece.