this heatsink is suitable for 540/550/3650 size motor, with a 4.8-6V cooling fan to protect your motor. The cooling fan can power up from the receiver, very easy to use. Dimensions of fan: Approx.1.18x1.18x0.39 inch/ 30x30x10mm Dimensions of cooling fin: Approx. 1.18x1.57 inch/ 30 x 40mm Total Height: 1.97 inch / 50mm Color: Blue Materials: metal Weight: 25g Package Contents: 1 X Aluminum Heat sink w/ 5V Cooling Fan Only the above package content, other products are not included. Note: Light shooting 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.