The Bach Trumpet Mouthpiece in Silver has been the standard since being created by trumpet master Vincent Bach. This series of Bach trumpet mouthpieces is available in a variety of sizes to meet the needs of the individual player.
The Bach mouthpiece numbering system is arranged in an orderly progression from the largest to smallest diameters numbered from low to high.
 
3C - Medium - 16.30 mm - Medium wide - Fairly large cup, good for all-around use.
5C - Medium - 16.25 mm - Medium wide -  For players with a strong embouchure who do not like a sharp edge. Well rounded toward the inside and outside, fairly flat.The tone is lively and rich.
7C - Medium - 16.20 mm  - Medium wide, lowered toward the outside, Medium sharp inside. Well-rounded edge with a perfect grip. Probably the most widely used model in the world. Its brilliant tone is preferred by school musicians and by artists.