Whether Jarno taper - which is a single taper that starts at zero and goes on forever - or a particular Morse taper that's almost exactly the same as Jarno, that's the taper that our screw shanks on our modular mouthpieces follow. We get some feedback occasionally that mouthpiece shanks don't quite seat perfectly in various individual tubas receivers. The machine that turns these out is really accurate, and it's just not practical to offer subtly different tapers, even though we offer different shank sizes (all along this same taper). From owning a bunch of tubas, I know that receivers can vary quite a bit. I've had to change receiver tapers on several of my own tubas in order to standardize them to receive mouthpieces for a perfect fit. It's not so easy for end users, because the reamer or the labor - depending on the method used to change the taper in a receiver - is either expensive or requires some delicate skills.
I've been talking with Dave, and we've decided to gradually replace exhausted inventories of stainless steel shanks with bronze shanks. This bronze aĺloy is harder than most brass alloys, and actually almost as hard as stainless steel, yet has properties whereby it's slightly more forgiving and hopefully will lodge in more of the slightly off-taper receivers without refusing to "conform" - for lack of a better term - to those slightly oddball receiver tapers (as they are legion, and - again - I've dealt with oddball receiver tapers with several of my own instruments).
Just as everyone else says who is trying to sell something, "This will have no effect on the sound."
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This has nothing to do with the silver plated brass one-piece mouthpieces promoted in another thread.
