How does your trombone sizing system work?

Edited

Pickett trombone mouthpieces follow a similar sizing system to other brands, such as Bach, where the smaller number represents a larger mouthpiece size. With 1 being the largest option and 15 being the smallest, there are a wide range of options available. For example, a Bach 5G would be closest to our 5M (medium cup) paired with a 5C (classic rim).