Open box. The Pro Check Sensor is a wireless propane tank magnetic sensor level indicator designed for outdoor use. It features an ultrasonic sensor for accurate fuel level monitoring and has an audible alarm to alert the user when the tank is low. This pro-style sensor comes with 1 sensor unit, 1 grease packet, and 3 metal spacers, all in a compact package measuring 5.87x4.53x0.67 inches. The sensor is battery-powered and includes 1 lithium metal cell, making it a convenient and reliable tool for camping and hiking trips.