Polyester, Teflon (FEP) and polyimide, and reinforced insulations were evaluated with respect to various mechanical, environmental, and thermal conditions. The materials exhibited good dimensional stability and roll flex life, in excess of 5000 cycles for Teflon and polyimide, and in excess of 3500 for polyester. One of the Teflon samples delaminated completely during aging (150 to 200°C). At room temperature and the aging temperatures, both noise and numerous discontinuities were encountered during vibration at resonant frequencies ranging between 40 and 550 hertz. At --65°C the performance of the cables was excellent with regard to roll flex life and vibration. An experimental reinforced insulated cable exhibited excellent mechanical and physical properties. Calculated and measured weight savings of fiat cable over round wire are tabulated together with cost savings achieved on a given prototype system. Methods of terminating and harnessing fiat cable are illustrated.