Abstract: A heat exchanger, especially a heat exchanger in the form of a comfort heat exchanger, is disclosed. The heat exchanger is comprised of two manifold elements adapted to receive and discharge fluid, and a plurality of tube units transversely located between the manifolds, each tube unit being integrally connected to substantially rigid end elements that fit into the manifolds. The tubes are preferably oriented and expanded to about their original diameter. The heat exchanger is intended to be fabricated from polymer, especially polyamide compositions. The tube units are intended to be manufactured using injection moulding techniques, and then subjected to orientation and expansion steps. Parts fabricated during manufacture of the heat exchangers are also disclosed. The heat exchangers are particularly intended for use as comfort heat exchangers in automobiles.