Nycticebus coucang is a small primate, measuring between 300 and 380 mm for head and body. Individuals typically weigh less than 2 kg.
Slow lorises have a vestigial tail. The second digit on their hands is reduced in size, and the big toe on the hind foot is set well apart from the other toes, demonstrating great gripping power. As in all lorisoids, slow lorises have a long, curved claw on the second toe which sticks up and is used to scratch the skin. Lorises have more vertebrae in their backs, giving them a greater tree-climbing advantage since they can twist around above and below branches with wide range and extension of movement.
Slow lorises are covered with short, thick, woolly fur, which is found in a wide variety of colors and patterns. Generally, the color above is from light brownish gray to deep reddish brown, sometimes with a hoary effect produced by the tips of individual hairs. The color beneath ranges from white to buffy to grayish. There is usually a dark mid-line along the neck and back, and a light streak between the orbital rings.
This species produces a toxin from brachial glands on its arms, and a toothcomb on the lower jaw may help the loris transfer the toxin (see other comments).
Range mass: 2 (high) kg.
Average mass: 0 kg.
Range length: 300 to 380 mm.
Average basal metabolic rate: 1.504 W.