Circular connectors are connectors with a circular shape that mate with an identical circular shape, typically male and female connectors. They are used in a variety of applications including electrical and mechanical, such as data transmission, government and military, and networking applications. Typically, the connectors are used to join two wires, or multiple wires, together with a mating surface, and may be constructed from plastic, metal or a combination of materials. Depending on their purpose, they may be single-contact, multi-contact or multi-pin. In single-contact connectors, the contact can be either a pin or a socket, while in the multi-contact designs, two or more contacts can be used. The most common types of circular connectors are D-subminiature connectors, RJ-connectors, MC-connectors and SC-connectors. They are widely used in automotive, aviation, aerospace, automation and many other industries.