776539-4 is an AMPSEAL 16 connector cap designed for 12-way electrical connections with D key keying and reduced diameter seal configuration. The connector features a black housing with a green polarization ring (PLR) for visual identification and proper mating orientation. With a contact size of 1.58 mm and 12 cavities, this cap connector is engineered for environmentally sealed applications in industrial and commercial transportation environments. The reduced diameter seal design provides enhanced sealing performance while maintaining compatibility with standard AMPSEAL 16 contact systems. This connector is commonly used in automotive, heavy equipment, and industrial control systems where reliable, sealed electrical connections are critical for durability and performance in harsh operating conditions.