The King 2280 soloist model Euphonium The King 2280 soloist model euphonium has established a new standard for tonal excellence and evenness of scale-the chief attributes of any serious euphonium. This model's duo-bore design (.580"/14.73mm in the first three valves and .600"/15.24mm in the fourth valve) and 11"/279mm seamless heavy yellow brass bell give it a uniquely lyrical sweetness in the upper register and a majestic resonance in the lower.