An insulator supporting an inner conductor within the outer conductor of a coaxial device formed from a portion of thermally conductive polymer composition with a thermal conductivity of at least 4 W/m-K. The portion is dimensioned with an outer diameter in contact with the outer conductor and a coaxial central bore supporting there through the inner conductor. Cavities may be formed in the portion for dielectric matching and or material conservation purposes. The insulator may be cost effectively fabricated via injection molding.