Whistler Tire Scout Ts-104 - Readout Units [[]psi[]] Reduce Driving Risks - Driving with under-inflated tires may cause uneven tire wear and poor respons Improve Fuel Economy - Today's tire designs make visual inspection of deflated tires very difficult. Prolong Tire Tread Life - Help prolong the life of your tires by keeping it at proper inflation pres Installation - Sensor comes with four tire sensors, which easily screw onto the end of the tire val