Rim – Common Requests:
Slightly flatten – To help rim “stick” to the chops better for high compression lead playing.
Round the inside radius – Softens the bite of a too sharp rim
Round the outside radius – relieves the feeling of being “pinned down” Creates more awareness of the inside diameter for more accurate attacks.

Cup – Common requests:
Create more “undercut” (more room just inside the cup). This is a common remedy for the player who has begun bottoming or touching inside a shallow mouthpiece.
Change cup shape by adding girth to the bowl for a broader sound without increasing the overall depth.

Throat Entrance – This area has a profound effect on performance. Often a bottlenecked or stuffy feeling can be eliminated without changing the bore (throat) size. A dead, dull sounding cup can often be brought to life by changing the shape of the throat entrance to a more linear V shape.