Abstract: The firewall feed-through adapter of the present invention, and method for making, is an assembly utilizing an aluminum oxide insulator which is specially machined to interfit with the outer insulation of the conductors. The firewall shell is specially designed to compress the insulator about the conductors and their wire insulation to insure a complete sealing of the firewall side of the adapter. The shell of the adapter is machined both to reduce the labor involved in its manufacture, as well as to provide an internal frusto-conic surface which is used to compress the insulation about the conductors and their wire insulation. The action of securing the shell to the back plate simultaneously seals the shell against the firewall while sealing the insulation against the conductors and the inner surfaces of the shell.