MIL-DTL-38999 Series I connectors feature up to 128 contacts in an insert, designed for harsh environments with an operating temperature range of -65 °C to 200 °C. Available in various shell sizes and insert arrangements, they offer front wall mount, rear wall mount, and jam nut receptacles, along with RFI grounding plugs. These connectors utilize M39029 rear release crimp contacts in sizes 22D, 22M, 22, 20, 16, and 8 (coax and twinax), ensuring secure connections. Constructed with high-strength aluminum shells, they come in plating options such as light iridescent yellow cadmium, olive drab cadmium, electroless nickel, and black anodized aluminum, with RoHS certified cadmium-free finishes available. Suitable for military and industrial applications, these circular receptacles are ideal for back panel and box mounting with bayonet coupling, providing reliable performance in demanding environments.