Feature : Solar charging board & USB Charging,high charging efficiency and durable. TPMS ensures proper tire pressure, which is necessary to ensure vehicle safety, handling, comfortable driving, and tire life. After installing the tire pressure monitoring system, it will remind you of the tire condition of the car in advance, and the system can monitor the tire pressure and temperature in real time. Build-in sensors and external sensors options, meets all your need. Colorful LCD Digital displaying, clear to show tire information. Rear-time monitoring pressure & temperature of 4 tires. If abnormal tire pressure and temperature are detected, the system will issue a real-time warning sound and light up the flashing icons on the screen to deal with problems in time to avoid traffic accidents. Button Function : Left Button : Long press to power on/off,Short press is Up/Previoufinction. M Button: Long press the "M"button and enter the settingmode after hearing the bi sound . Short press the "M "button is confirm fuction. Right Button: Short Press is "'"Down/Next,Long press will back to main menu. Internal Sensor: Working pressure: 0 - 81 psi / 0 - 5.6 bar - Pressure accuracy: plus or minus 1.5 psi - Transmission frequency: 433.92MHz - Working temperature: - 20 - 85 Deg.C - Storage temperature: -40 - 125 Deg.C - Working voltage: 2.0 - 3.6V - Waterproof grade: IP67 - Battery: built-in CR2450 button - Battery life: 2 - 5 years External Sensor: Working pressure: 0 - 81 psi / 0 - 5.6 bar - Pressure accuracy: +/- 1.5 psi - Operating frequency: 433.92MHz - Working voltage: 2.0 - 3.6V - Waterproof: IP67 - Working temperature:-40 - 85 Deg.C - Storage temperature:-40 - 125 Deg.C - Battery: built-in CR1632 button - Battery life: 1-2 years (can replace battery) TPMS Receiver: Battery: built-in 400mAh Li-ion battery - Operating voltage: DC 5V - RF transmission frequency: 433.92MHz - Pressure unit: Psi/bar - Temperature unit: Deg.C / Deg.F - Operating temperature: -20 - 85 Deg.C - Storage temperature: -40 - 125 Deg.C Package Included 1 Set External sensors/ Internal sensors Do drop