The cap is a simple cap that cools the Pi and gives it a safe shutdown button. With just one line of writing, you will have the full functionality of the hat, allowing you to do additional features like restarting the pi and adjusting the fan speed of the single board computer. You can even program when the fan adjusts its speed, giving you full control of the hat. Use it on any case that offers hat support, such as + or NEO. The best part is that it will work for the 4 Model B, 3 Model B, and 3 B +. You can change the fan speed according to the CPU temperature. Provides enough space to use heat sink on board chips. colour: black Material: plastic size: 65x57mm Package Contents: 1 x Fan HAT 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.