The Tuba Mouthpiece Page is now online. You can see various makers' specifications such as cup width, throat size, cup depth, rim width, etc., and you can limit the view to mouthpieces of similar size to one you use or one are interested in. As for any such comparisons, the numbers and descriptions do not tell the whole story. You still need to try a mouthpiece to know if it is a good choice for you. But this page might help you narrow the field or let you know of other brands ...