An unripe Gac fruit, also known Spiny Bitter Gourd, and in Thai as fak khao. It grows to the size of an adult hand, is round or oblong, and its exterior skin is covered in small spines. Initially the thick skin is yellow, but becomes a dark orange upon ripening (fig.).

On the inside, ripe fruits have dark red aril surrounding the seeds, which in Vietnam is used to prepare a dish of sticky rice known as xoi gac (fig.). This one was found growing from a vine in the wild, in Kanchanaburi province.