Heat sink provides long lasting usage, it will help dissipate the heat and protect your relay. Easy installation: Made of aluminum material, mountable heatsink design, compact size, easy to install.need to be evenly coated with thermal grease between the solid state relay and the heat sink. Calculated calorific value: Actual load current (Amps) x1.5 watts / Ampere. Fit for: solid state relay -10A,25A,40A. The temperature of the solid state relay and the Radiator Module (contact with the heat sink) must not exceed 80 Celsius. Product name: aluminum heat sink. Size: 8*5*5cm colour: black Material: aluminum Note: the solid state relay is not included. Package Contents: 3*Solid State Relay Heat Sink 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.