The bass trombone is a specialty instrument used within a section of several trombones in a band, orchestra or brass choir.  Pitched in Bb with one or two valves extending to F and D, they have some characteristics of the large bore tenor trombones, but their agility and extended low range make them a solo instrument in their own right.

I apologize for the low stock.  One maker changed the design to our detriment, two other makers have a one year wait for an instrument, other brands are now found in the big box stores. - SF