From the manufacturer:
Vincent Bach was a rare combination of artist and engineer. He constantly changed his mouthpieces in search of the perfect design. It wasn't until the mid 1960's that he stopped and finally settled on more standardized design. It was around this time that the formalization of the 27 throat and backbore to cup letter (A=24, B=7, C= 10, etc.) created a standard for mouthpiece making that is still used today. These standards are now known as the Classic Series.
- 1: Extra-large cup for players with a robust embouchure. Produces a great volume of tone.
- 1X: The pre-1970 (old style) No. 1, with slightly smaller cu and wider rim than the present model.
- 1B: Large cup for players with a robust embouchure. Produces a warm tone with great volume.
- 1C: Large diameter, medium cup - good for all-around use.
- 1CW: Same as No. 1C with wider cushion rim.
- 1D: Medium-shallow cup facilitates a brilliant tone and easier access to the high register.
- 1E: Facilitates high register with a shallow cup and medium-wide rim.
- 1 1/4 C: Large cup for powerful trumpeters. Compact tone of great carrying power.
- 1 1/2 C: Large diameter (17mm), medium cup - good for all-around use.
- 3C: Fairly large cup, 16.3mm rim, good for all-around use.
- 5C: For players with a strong embouchure who do not like a sharp edge. The tone is lively and rich. 16.25mm diameter.