Balaenoptera physalus is a baleen whale and can be recognised as such by the plates of baleen (rather than teeth) suspended from the upper jaw and the two blowholes on the upper body. The fin whale is slender bodied and can reach up to 24 m in length. It is a member of the rorqual family with the characteristic ventral pleats of skin under the eye and the relatively flat and broad jaw. The ventral pleats extend beyond the navel. The small flippers are less than one-fifth of the body length. It has only one prominent ridge on the snout. The head is pointed and V-shaped, the dorsal fin is a moderate size and set less far back on the body, and the head colouration is asymmetrical. The fin whale has a dark dorsal and lateral colouration with light streaks and the belly is white. The left side of the head is grey, while much of the right side is white in colour.