The DIY tyre pressure monitoring system from Steel Mate comes with 4 external screw on sensors and a cigarette plug in display which makes for easy installation.The cigarette plug is able to display the current tyre pressures for each tyre and allows the user to scroll through each tyre pressure and displays the pressure in PSI. The plug in cigarette also has audible and visual warnings that are displayed when a tyre pressure drops below or raises above the recommended level.Each sensor is pre paired to the correct wheel position and labelled to ensure easy installation, each sensor simply screws on to the valve stem and then is locked in place with the provided locknut tool.Each sensor is powered by a 3V battery to ensure long life.Sensors:Operating Frequency: 433.92MHzBattery Voltage: 3VBattery Type: CR1632Operating Temperature: -20°C -+ 60°CPressure Range: 0-3.5 Bar / 0-50 PsiHigh Pressure Value: 3.3 Bar/47 PsiLow Pressure Value: 1.7 Bar/25 Psi