IUGNF66-1-51-20.0 is a hydraulic magnetic circuit protector from the IAG/IUG/IEG/CEG/LEG series manufactured by Airpax/Sensata Technologies, providing low-cost power switching and accurate circuit control for equipment in the international marketplace. This unit features a 20.0-ampere current rating with delay type 66 (medium-long delay characteristic), operating at 240Vac maximum and 80Vdc maximum for 50-60Hz applications. The protector is available in series configuration with screw terminals (M5 x 5mm for ratings above 30A), and includes operating life exceeding 10,000 operations at 6 operations per minute when tested at rated current plus no-load conditions. The device meets MIL-PRF-55629 requirements for moisture resistance and salt spray corrosion, with shock and vibration performance verified per MIL-STD-202 standards. Common applications include industrial automation systems, sensitive circuitry protection, and equipment requiring reliable overload and short-circuit protection with customizable delay characteristics.