Our Digital In Cab Compressor Kit has a twin LED display and electric push button switches beside the gauge, operating 4 electronic valves outside the car - 1 up and 1 down for each bag. This means no air lines inside the car, and a reduced risk of springing an air leak with a lot less air fittings.  The ability to inflate and deflate each bag even while driving is a huge advantage. It means you can get the pressures just how you like them depending upon your load or the driving conditions. Contractors who's load changes weights as the day goes on can quickly adjust the bags as they go with the tickle of a button.