being a brass player (for a couple months) then you recognize the importance and variance between certain design characteristics in brass mouthpieces =-). Such as with the depth of the cup; rim shape; throat; and backbore. Here's is Selmers summary on all that:
In choosing a special combination of rim, cup, throat, and
backbore designs, consider the effects of the following:
Rim shape
Wide: Increases endurance
Narrow: Improves flexibility, range
Round: Improves comfort
Sharp: Increases brilliance, precision of attack
Cup size
Large: Increases volume, control
Small: Relieves fatigue, weakness
Cup depth
Deep: Darkens tone, especially in low register
Shallow: Brightens tone, improves response, 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, identifying backbores by size isnt possible, because they also vary in shape. Various combinations of size and shape darken or brighten the tone, 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 with the backbore.
So in that essense woodwind mouthpieces are no different. They are designed for certain characteristics and not all mouthpeices fit well with the players and not all fit well with the instruments.
well, at least your cousin may recognize the differences