Last one! This line is discontinued.
The Holton TR181 inline independent double rotor bass trombone is reputed to have established the true bass trombone sound, and is ideal for both symphonic and solo performance.
Its ten-inch red brass bell is styled to maintain a consistent, warm timbre across the dynamic range. The unique G/G-flat attachment can be reconfigured to the player's taste for setting up low C and B-natural.
Along with a larger bore and bell diameter, bass trombones are often equipped with a second rotor to extend their low register. There are two double-rotor systems: ‘independent’ and ‘dependent’. An independent system has both rotors sitting side-by-side (or ‘inline’) on the neck-pipe, where they can function alone or in tandem. Dependent models locate the second rotor on the F attachment rather than the neck-pipe, hence the alternative descriptors ‘stacked’ or ‘offset’. In this configuration, use of the second rotor depends on the first rotor being simultaneously engaged.
Manufacturer’s website: conn-selmer.eu