D38999/26FC4SN is a MIL-DTL-38999 Series III straight plug connector designed for rugged, harsh environment subminiature applications in aerospace, defense, and marine industries. The connector features a stainless steel shell with passivated finish (K-class) providing 500-hour salt spray corrosion resistance, and employs a threaded 360° turn coupling mechanism for secure mating. It incorporates environmentally sealed design with optional spring fingers for EMI control, scoop-proof construction, and supports AS39029 contact types in crimp, solder cup, or PCB tail styles. The connector operates reliably across a wide temperature range of -65°C to +150°C and is rated for 500 mating cycles, with higher durability versions available. This configuration is ideal for applications requiring robust electrical connectivity in demanding environments where environmental sealing and corrosion resistance are critical.