This report is the result of a study to develop heat-resistant fin materials possessing a high thermal conductivity for air radiators. Since an economical and commercially feasible product was desired, the investigation was restricted primarily to a study of electroplated copper, clad copper, and copper alloys. Sheet material 0.008 to 0.010 in. thick was evaluated for fabricability and for metallurgical stability and thermal conductivity at 1500°F. From the results of the rests it was concluded that: (1) electroplates were unsatisfactory; (2) clad-copper fins possessing a thermal conductivity of 50% of that of copper are commercially feasible; (3) copper-aluminum alloys possessing a thermal conductivity approaching that of copper at 1500°F are possible. Service tests of clad copper and the copper-aluminum alloys indicate that the choice of materials will be dictated by the requirements of the radiator, since each presents some unique problems.