All bats have the same general shape and wing structure, but they vary considerably in size. The largest bats have a wingspan of about 5 feet (1.5 meters) and a weight of about 2.2 pounds (1 kilogram). One of the smallest bats has a wingspan of barely 6 inches (15 centimeters) and weighs about 0.07 ounce (about 2 grams).
Bats vary in color and in fur texture. They generally have shades of brown, tan, gray, or black on top and lighter shades on the underside. Red, yellow, or orange variations occur in many species. Speckled or mottled patterns are common, as are bright or light-colored spots or stripes.
The chest and shoulders of bats are large and strong to provide power to the wings, which are generally dark and hairless. The thumb, always free of the wing, is used for walking or climbing in some species; in others it is used for handling food. Only the thumb—and occasionally the index finger—ends with a claw. Bats that walk often have pads or suction disks on their thumbs or wrists or both. The legs and feet are only strong enough to hold on when hanging upside down from a perch, which is how bats rest or sleep. Some bats have tails, while others are tailless.
Bats often have muzzles that resemble rodents or foxes, but in many the face has a pushed-in pug-nosed appearance. Many bats have a fleshy piece of skin called the nose leaf surrounding the nostrils. Scientists believe that this flap may help to direct the bats' outgoing calls. The ears are generally large, which probably helps them detect incoming signals.