Alto trombone 36H Symphony. C.G. Conn Instruments standing for high quality american made brass instruments. The history shows the long periode of making experiences and getting better. But the main effort based on passion and love for music. Play and you will hear it. Features Bb rotor attachment, Dual bore .491"/500" = 12,47/12,70 mm, Bell Ø 7" = 178 mm, Hand-hammered one-piece bell, Chrome-plated nickel-silver inner slides, Wood shell case, Lacquered finish.