I am using this mouthpiece with a Besson Prestige, after getting back into playing the euphonium following a 20+ year layoff. I started for the first few months with an SM2U which I really liked but in the end, needed a little more help with the upper register. The SM3X seems to have the same nicely matched response to the Prestige as the bigger mouthpiece but I've found it has been an easier playing mouthpiece to use up and down the range with quite possibly more duration through a long blow too and it's become my first choice now. Usual Denis Wick quality, I'm sure unless I am careless it will see me out to the end of my playing days (an easier thing to say now than when I bought my first Denis Wick, a 4AM, 42 years ago).