The rim diameter of the 24 is rather small but the "A" cup is a huge bowl which actually gets wider inside the bowl that at the rim itself. The W notates the wide cushion-style rim.iiipopes wrote:One interesting note: as far as Kelly goes, they have made the cup of their 18 deeper than a Bach 18. It is almost as deep as the Conn Helleberg. But it does still have the rounded bottom, and others as well as I can definitely tell the difference in tone between it and my Wick 1, which also has the Helleberg style cup, but with a Bach-ish rim.
A second interesting note: yes, the 24AW is technically a smaller diameter cup than the 18, but to a lot of people it feels not only more comfortable, but larger due to the much wider rim. This is one example where specs are not the be-all and end-all to picking a tuba mouthpiece. The specs get you in the ball park, or now with so many manufacturers, out of wandering the whole universe to (hopefully!) a single galaxy, so you can try several that are similar and up, down or sideways a notch to help you narrow down to your final choice(s).
ken k