HDK 1.2 & 2.8 Connection System Aptiv HDK 1.2 and 2.8 Connection System are automotive connectors with a vibration resistance of 60g and the uniform configuration of USCAR and AK standards. Aptiv HDK Connection System includes connectors, terminals, seals, and wire strain reliefs. The series is available in cavity configurations of 1.2mm and 2.8mm. Contacts range from two to four contacts.