I have a Wessex 4Y euphonium mouthpiece that seems to be related to the tuba mouthpieces of Dr. Frederick Young. I find it extremely acoustically efficient, with great clarity, stability, and flexibility. The closest "feel" companion to it in my personal mpc stable is a Denis Wick 4ABL. Differences seem to be primarily in the "airflow", likely due to the more cone-like shape of the cup and the absolute freedom of the backbore. It has about a 1.03" inner cup diameter with about a .290" venturi, with apparently a "straight-through" exhaust system. There is one of these in my Besson 967 Sovereign now. HALLELUJAH!: