Abstract: A medical device for implantation in tissue includes: a header including one or more bores, the header including an implant grade thermoplastic resin including a conductive additive and a metal coating; one or more leads disposed in the header and exiting the header through the one or more bores; and an enclosure coupled to the header at a surface of the enclosure, the enclosure including circuitry and a power source. A sterilized header for an implantable enclosure is also described.