The TPS10-4E Tyre Pressure Monitoring System includes 4 External sensors| but has the capability of simultaneously running up to 10 sensors through the solar powered LCD display unit. This unit is the perfect solution for those with a towing vehicle and caravan/boat/camper or box trailer. TPMS in Australia are being used increasingly as safety devices| and with more people jumping in their vehicle to head around Australia and tap into the amazing playground we all call home| accurately reviewing a vehicles tyre pressure in an instant| minimises the risk of tyre failure leading to disaster| while at the same time| positively affecting the handling of the vehicle. Ensuring the tyre’s are optimally inflated will also positively affect the fuel economy of a vehicle. NOTE: TPS10 EXTERNAL sensor model is not compatible with TPS10 INTERNAL sensor model