Blusmart Waterproof Bicycle Computer 27-functions with Clock Stopwatch Thermometer Wired Bike Speedometer of LCD Backlight Big Screen Wired transmission between the sensor and unit, strong electromagnetic Anti-interference ability, to ensure accurate riding records, such as Current/Average/Max speed, Trip/Total Distance, Temperature and Clock, etc. Includes backlight screen for clear viewing even at night, the backlight mode is on or off when you press any button during 6:00 PM to 6:00 AM; Waterproof feature, you dont have to worry about riding in a rainy day, but don't put in the rainstorm or soak in water for a long time. Sleep mode and automatic wake-up, humanized and also energy-efficient. If no signal has been inputted for 300 seconds, computer will enter into Sleep mode, CLK remains. Easily and securely to install. Its lightweight, durable design, and comprehensive riding records, making your riding life more convenient and funny. Simple tire size setup appears on the screen when the battery has been installed, with one figure flashing, choose the correct wheel circumference from the table of user manual.The sensor wire measurement is 33 inch.