The modern bass trombone is pitched in B. It has the same length of tubing as the tenor trombone () but has a wider bore and a larger bell, and uses a larger mouthpiece, making it more suited to playing in the low register. Typical specifications would be a bore size of in the slide and through the valve attachment tubing, with a bell from in diameter. Modern bass trombones have one or (more commonly) two valves which, when engaged, lower the pitch of the instrument. The first valve lowers the key of the instrument to F. There are two types of second valve—one type lowers the key to G, the other, less common, type lowers it to G. An instrument with two valves may be configured in either a dependent or independent system. In a dependent system, the second valve can only be engaged when the first valve is engaged—this combination lowers the key to either E or D. In an independent system the valves can be used individually or in tandem. Bass trombones from the 19th- and early 20th-century were sometimes made with a valve attachment in E rather than F, or with an alternative tuning slide to lower the pitch to E. Bass trombones with one valve often have a tuning slide that is long enough to lower the pitch by an additional half-step, changing the key to E instead of F.