Abstract: A fluid-tight electrical coupling for a medical device fully implantable in the body of a recipient, such as an implantable defibrillator, is disclosed. The fluid-tight coupling is mounted on a hermetically sealed casing. The coupling comprises a housing having receptacles for receiving an electrical conductor plug. Terminal blocks are provided within the housing and define a pin opening for receiving the pins of the electrical conductor plug. The terminal block is electrically connected to the exterior of the housing. The terminal block also includes a cylindrically shaped boss extending from a face of the terminal block. The boss is externally and internally threaded for receiving a sealing cap and a retaining member respectively. The retaining member comprises a hexagonal socket head set screw. The sealing cap seals off the interior of the housing. The sealing cap is secured to the terminal block to seal off the housing opening by means of a screwdriver that is adapted to retain the sealing cap thereto.