WMF21 series thermistors are designed to limit inrush current in the power supply circuits of various electronic devices, including switching power supplies, UPS systems, and CFL lamps, as well as in the heating circuits of CRT color TVs, monitors, heaters, and filaments. This series features a leaded resin-coated construction, offering a compact size, high power handling, strong inrush current suppression, fast response time, and high reliability. The thermistor's material constant (B) increases as temperature decreases, while residual resistance decreases. Higher thermal capacity results in improved inrush current limiting performance, which is directly proportional to the product of the thermal time constant (T) and the thermal dissipation constant (). The WMF21 series is widely used in switching power supplies, UPS systems, CFLs, and general power supply circuits. Color: Black Material: Metal Package contents: 1 x Thermistor Note: Lighting and display settings may cause slight variations in color representation. Measurement tolerances may vary by 13 cm.