Zacro Bike Computer,Original Wireless Bicycle Speedometer with Compass Key Ring Easy-to-read LCD display : big LCD display with big numbers so you can easily see the stats even you are riding. Please note the slight rattle sound from device is normal phenomenon, which results from the design of automatic function. Portable and convenient: It is very small and light but you can have the basic info you need in monitoring your biking activity, measuring speed ,distance, riding time, maximum speed and average speed.A must-have for cyclists. Wireless and water resistant design: You attach the sensors to your front fork and your spokes and you're good to go. Long gone are the days of a bunch of ugly, tangled wires on your handlebars, and you do not need to worry about raining. The backlight can be set in either green and white color. Built-in steel ball switch that will shake when receiving signals, computer will be automatic awake from sleeping mode. Meanwhile you may hear slight rattle from the device. It's common phenomenon as steel ball is working. No worry about it. Bonus: Besides the fact that it is suitable to all types of bicycles: road cycling, mountain biking, folding bike, common bicycle, We have also attached a Compass key ring as a free gift.