MADE up of a series of Tubes and Cooling Fins which run along the length of the radiator.When the radiator is in use, coolant flows from TANK to tank VIA the tubes in the core allowing it to dissipate heat through the tube walls and the fins.The core can be made in two ways:Tube and fin coresCellular or film type coresThere are two types of tubes which are used in the radiator:Aluminum tubes: These are used in modern radiators and tanks are made of PLASTIC with aluminum.BRASS tubes: With the use of brass tubes, tank is also made of brass.