Gibbons, specifically the Siamang (Symphalangus syndactylus), are a robustly built species among the 10 other species in the family Hylobatidae. Measuring 75-90 cm (29.5-35.4 in) long and weighing 8-13 kg (17.6-28.6 lbs), S. syndactylus possesses an arm-spread of 1.5 m (almost 5 ft). S. syndactylus is black in color with a longer, thinner coat than other species. The Siamang is distinguished by a large, hairless, empty air sac on the front of their throats that inflates during vocalization, and by webbing between their second and third toes. S. syndactylus, like other gibbon species, are brachiators, meaning that they travel through the trees by swinging with their arms. The Siamang is an omnivore, but fruit is their main dietary focus.