Tree 5-25 m. Leaves membranous or thinly coriaceous, elliptic-oblong to lanceolate, (5-)8-25 by 2-5(-8.5) cm, base attenuate, rarely rounded, apex acute-acuminate, drying greenish or brown, often with a very fine-pitted structure a'bove, (lens!), lower surface greyish, with a reddish tinge, glabrescent except for the basal part of the midrib with farinose stellate scale-like hairs; Inflorescences: Fruits 1-4 per infructescence, ellipsoid, base and apex obtuse or subacute, 1.1-2.1 by 1.2-2 cm, with mealy yellowish brown or rusty hairs 0.2 mm long;
Asia-Tropical: Malaya (Peninsular Malaysia present, Singapore present), E Coast present, Johore present, Kedah present, Kelantan present, N Sumatra present, Pahang present, Penang I present, Simeuluë I present, Tapanuli present, Trengganu present
Malesia: N Sumatra ( E Coast, Tapanuli, Simeuluë I.), Peninsular Malaysia (Kedah, Kelantan, Trengganu, Pahang, Johore, Penang I.), Singapore.
Knema rubens is characterized by the more or less flattened twig apices, which also occur in K luteola and K. oblongifolia; it resembles in appearance K. latericia subsp. ridleyi which differs in the scaly bark of the (subterete) twigs, more pronounced convex staminal disc, and thicker indumentum on twigs and flowers.