The body of the contrabassoon is composed of six parts:
Crook or bocal: an S-shaped, thin piece of metal tubing as on the bassoon;
Metal shank: a roughly 90 cm long, U-shaped metal tube containing three holes for the speaker keys. On the underside of the bend there is a key for releasing condensation (water key). The U-shaped bend can sometimes be pulled out and used as a tuning slide;
Wing joint: made of maple;
Middle joint: made of maple, in two parts;
Long joint: made of maple, in two parts;
Bell: a straight wooden piece of tubing, pointing upward (C bell); can be replaced by a flaring, curved, metal bell that points downward (A bell).
The contrabassoon is therefore composed of four parallel pieces of tubing, the metal shank, wing joint, middle joint and long joint, plus the bell. These four parts are connected by three U-shaped pieces of metal tubing. With the C bell (lowest note Bb0) the tubing is about 550 cm long, with the A bell (lowest note A0) about 610 cm. Unlike the bassoon the contrabassoon has no boot.
As on the bassoon the double-reed mouthpiece is attached to the bocal. The reeds are larger than the bassoon’s: 7–7.5 cm long and 1.6–1.8 cm wide at the blowing end.
Nowadays the contrabassoon is made almost exclusively according to the Heckel system (also known as the German system) and has about 21 tone holes, all of which are closed by keys. There are no finger-holes covered by the fingers as on the bassoon.