Colour:black material:metal Package Contents: 4xthermistor Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. The WMF21 series thermistors has so wide application area, which is mainly used in Switching Power Supply, UPS Power Supply, CFL, Ballast, Circuitry of Power Supply, etc. The WMF21 series thermistors is the radial leads resin coating type products, it has the characteristic of small bulk, high power, strong limiting of inrush current, quick response, , high reliability, etc. The temperature is decreased while the Material Consistent(B) of thermisters is increasing and the Remain Resistance is decreasing. The higher is the Thermal Capacity, the stronger is the capability of limiting the Inrush Current. It is direct proportion to the product of the Thermal Time Constant (T) and Thermal Dissipation Constant (d) . WMF21 series thermistors are used for limiting the Inrush Current in the power supply loop of every kinds of power supply, ballast / CFL etc. and the heating loop of CRT of color TV / monitor, heater, filament etc.