MIL-DTL-38999 Series I connectors feature up to 128 contacts housed in an environmentally sealed insert, designed for harsh environments with an operating temperature range of -65 °C to 200 °C. This connector family includes front wall mount, rear wall mount, and jam nut receptacles, along with RFI grounding plugs, offering versatility in installation. With 9 shell sizes and 52 insert arrangements available, they utilize M39029 rear release crimp contacts in various sizes, including coax and twinax. Constructed with high-strength aluminum shells, these connectors come in different plating options such as light iridescent yellow cadmium, olive drab cadmium, electroless nickel, and black anodized aluminum, with RoHS compliant finishes. Suitable for military and industrial applications, they ensure reliable performance with features like bayonet coupling, removable crimp contacts, and conductive pins. The Series I connectors are specified for back panel wall mounting receptacles, with a service rating of II for environment resistance, making them ideal for demanding operational conditions.