This series features an inline double independent standard wrap rotor design in the key of Bb/ F / Gb and D with tapered bearings and precision linkage for outstanding performance plus a .562-inch bore for excellent response. The 740 Series also features a 10-inch bell available in yellow or rose brass designed for excellent resonance and projection. Bass Trombones Quality craftsmanship, computer-aided design, and contact with leading educators and artists contribute to the sound and playability of Jupiter instruments.