Patent-leather beetles in the family Passalidae are a group of large, shiny, and often dark-colored beetles known for their smooth, glossy exoskeleton that gives them their characteristic "patent-leather" appearance. Patent-leather beetles in the family Passalidae are generally large beetles, often measuring between 2.5 cm to 4 cm (1 to 1.5 inches) in length, though some species can be even larger.