MC3 connectors are a type of single contact connector commonly used for connecting photovoltaic panels. MC3 stands for "Multi Contact" with a 3mm² contact assembly pin. They are typically rated at 20 ampere and 600 volts maximum (UL). (conductor size used and rating system dependant).
The MC3 connectors incorporate a flexible watertight seal and are supplied as 'male' and 'female' types to minimise the chance of wrong connections. For proper application usage, they are connected with UV resistant, correct diameter cable. The connector pairs hold together by friction and suction, only.
MC3 connectors have been largely superseded by MC4 connectors due to support being withdrawn by the NEC for solar applications. The MC3 connector does not incorporate a positive locking mechanism and can become disconnected unfavourably.