The Helleberg euphonium mouthpiece is a classic design in a diminutive size. This 5E has a deep cup, medium round rim and bass shank. Finished in silver or gold plate, includes mouthpiece brush. Made in Germany.
Comparison of size between Schilke 51D and Helleberg 5E...
diameter 25.55mm - published
backbore Schilke C - published
backbore - approx same as Schilke, but the Schilke is straighter with a flare at the end while the 5E is conical all the way through the shank. Like a 52E2-ish size but lighter.