More often than not, tenor trombones with an F attachment, or trigger, have a larger bore through the attachment than through the 'straight' section (the portion of the trombone through which the air flows when the attachment is not engaged). Typically, for orchestral instruments, the slide bore is and the attachment tubing bore is . A wide variety of valve attachments and combinations are available. Valve attachment tubing usually incorporates a small tuning slide so that the attachment tubing can be tuned separately from the rest of the instrument. Most B/F tenor and bass trombones include a tuning slide long enough to lower the pitch to E with the valve tubing engaged, enabling the production of B2.