Chris Hite, Tuba Specialist, makes a mouthpiece recommendation for primarily the high school tubist: What's beyond your basic Helleberg?
When discussing the Symphonic Concert line of mouthpieces for school bands, my first and strongest recommendation is the RT-48. It is closest to the Conn-Helleberg (CH) 120 but has a more comfortable rim and less bite which allows extended playing without fatigue or injury while still maintaining the seal and good articulations. The rim on the CH 120 is very flat and the bite often uncomfortable to the player. The shank size of the 48 is slightly reduced as compared to the rest of the RT line to fit into more student tubas with smaller receivers.
If I were to recommend two more models to offer some variations, they would be the RT-36 and RT-50. The 36 has a narrow rim diameter compared to the 48. It also has reduced cup volume for players with smaller facial features and/or weaker fundamentals. The 50 is bigger than the 48 and is meant for stronger players. It is the largest RT mouthpiece with a funnel-shaped cup and provides a big sound but requires firm corners of the embouchure. The shanks on both these models are larger (designed to fit B&S tubas) and should be checked in the receiver before purchase.
When one looks at the entire RT mouthpiece line, he or she will notice a lot of variations and some may seem minuscule or inconsequential but they can be the make-or-break detail for a player and the instrument of which they seek to pair a mouthpiece.
There are lots of brands and models of tuba mouthpieces available and many are of very high quality and often price. Robert Tucci (maker of RT mouthpieces) has sought to produce a line of mouthpieces that is of the highest quality and consistency available anywhere. He also strives to keep the price for the customer at a responsible level. Whether a student or professional purchases a RT mouthpiece, they will be ensured to possess a tool of the highest caliber and allow them to make the best music possible.