The trombone consists of three parts: the bell with the tuning slide; the inner slide, open at the top and bottom with the mouthpipe and mouthpiece attached to its top part and the bell attached to its bottom; and the U-shaped movable outer slide, which connects the two open-ended parallel tubes of the inner slide. Slide stays strengthen the two sets of parallel tubes. The main (inner) tube is held with the left hand and the slide shifted by the right, thus altering the tube length. It is the slide that distinguishes the trombone, the oldest brass wind instrument with a chromatic scale, from all the other brass instruments.
In France somewhat smaller bores are used than in Germany and North America, and smaller bores are also generally preferred for solo performances.