The very large D cup is excellent for the strong player. It is particularly suited for the Euphonium & Baritone, producing a full dark tone. This trombone mouthpiece has a 25.55-millimeter, medium-large cup, which delivers a dark, robust tone with plenty of volume. The Schilke 51D’s standard rim shape promotes comfort and stability. The 51D is also well suited for euphonium players.