Tuba

The tuba is a brass instrument that has the largest tube, therefor it hs the lowest pitch between them. Its tube is also long and it's wrapped in an elliptical form, where you can find the pistons.

A bit of history...

As one of the newest instrument in the brass group, its format hasn't changed much over the time. The tuba is also used in jazz bands and in the symphonic orchestra since it appeared.