Heater core (matrix) for Mk1 classic Minis with recirculating-type heater.

The recirculating heater was so-called because it received air only from the cabin, and did not have a duct supplying it with fresh air from outside the vehicle. It is most commonly to be found on very early Minis, since it was gradually phased out from 1963 onwards. Water inlet and outlet tubes are 6" apart, center to center.