MIL-DTL-38999 Series II connectors are designed for harsh environments, featuring up to 128 contacts in an insert with environmental sealing. Operating between -65°C and 200°C, these connectors come in various mounting options like front wall, rear wall, jam nut, and box mount receptacles. Available in 9 shell sizes and 52 insert arrangements, they use M39029 rear release crimp contacts in sizes 22D, 22M, 22, 20, 16, and 12. Constructed with aluminum shells, they offer plating choices such as cadmium finishes and electroless nickel. With a bayonet coupling and gold contact plating, these connectors ensure reliability with a mating life of 500 cycles, making them ideal for environment-resistant applications.