Yamaha YBB-632S Bb TubaThe design incorporates a large 500mm diameter bell that keeps the sound focused and always clear. They deliver a rich tone and abundant volume that provides the ensemble with a solid and stable foundation. Large Diameter Bell At 500mm, this is the largest bell among Yamaha BBb basses. Its size greatly improves dynamic range while delivering a stable sound that envelops the entire ensemble. Bore Size The bore size offers freer blowing with a moderate