Rim
Wide: Increases endurance.
Narrow: Improves flexibility, range.
Round: Improves comfort.
Sharp: Increases brilliance, precision of attack.
Cup
Large: Increases volume, control.
Small: Relieves fatigue, weakness.
Deep: Darkens tone, especially in low register.
Shallow: Brightens tone, improvesresponse, especially in high register.
Throat
Large: Increases blowing freedom, volume, tone; sharpens high register (largest sizes also sharpen low register).
Small: Increases resistance, endurance, brilliance; flattens high register.
Backbore
Except in general terms, it isn’t possible to identify backbores by size because they also vary in shape. Various combinations of size and shape make the tone darker or more brilliant, raise or lower the pitch in one or more registers, increase or decrease volume. In each instance, the effect depends in part on the throat and cup used in combination with the backbore.