WMF21 series thermistors are used to limit inrush current in the power supply loop of various types of power supplies, CFLs, etc., and the heating loop in CRT color TVs/monitors, heaters, filaments, etc. WMF21 series thermistors are leaded resin-coated, featuring small size, high power, strong inrush current limitation, fast response, and high reliability. The temperature decreases as the material (B) in the thermistors increases and the residual resistance decreases. The higher the heat capacity, the stronger the ability to limit inrush current. It is directly proportional to the product of the thermal time constant (T) and the thermal power loss constant (d). WMF21 series thermistors have a wide range of applications and are mainly used in switched-mode power supplies, UPS power supplies, CFLs, and power supply circuits. Color: black Material: metal Package contents: 1 * thermistor