As the name suggests, there is no coxswain (cox) on such a boat, and the two rowers co-ordinate steering and the proper timing of oar strokes between themselves or by means of a steering installation which is operated by foot from one of the rowers.
Racing boats (often called "shells") are long, narrow, and broadly semi-circular in cross-section in order to reduce drag to a minimum.
Pairs have a fin towards the rear, to help prevent roll and yaw.
A coxless pair is often considered the most difficult boat to row, as each rower must balance their side in cooperation with the other, apply equal power, place their catch and extract the blade simultaneously in order to move the boat efficiently.
"Coxless pair" is one of the classes recognized by the International Rowing Federation and is competed in the Olympic Games.