MIL-DTL-38999 Series I connectors offer rugged performance with up to 128 contacts in an environmentally sealed insert. Operating in extreme temperatures from -65 °C to 200 °C, these connectors feature front wall mount, rear wall mount, and jam nut receptacles, along with RFI grounding plugs. With 9 shell sizes and 52 insert arrangements, they utilize M39029 rear release crimp contacts in various sizes. Constructed with high-strength aluminum shells, they come in plating options like electroless nickel and cadmium finishes, including RoHS certified cadmium-free variants. Designed for military specifications, these circular receptacles ensure reliable connectivity in demanding environments.