Although flightless, emus have vestigial wings, the wing chord measuring around , and each wing having a small claw at the tip. Emus flap their wings when running, perhaps as a means of stabilising themselves when moving fast. They have long necks and legs, and can run at speeds of due to their highly specialised pelvic limb musculature. Their feet have only three toes and a similarly reduced number of bones and associated foot muscles; emus are unique among birds in that their gastrocnemius muscles in the back of the lower legs have four bellies instead of the usual three. The pelvic limb muscles of emus contribute a similar proportion of the total body mass as do the flight muscles of flying birds. When walking, the emu takes strides of about , but at full gallop, a stride can be as long as . Its legs are devoid of feathers and underneath its feet are thick, cushioned pads. Like the cassowary, the emu has sharp claws on its toes which are its major defensive attribute, and are used in combat to inflict wounds on opponents by kicking. The toe and claw total in length. The bill is quite small, measuring , and is soft, being adapted for grazing. Emus have good eyesight and hearing, which allows them to detect threats at some distance.