The PRO Sensor combines all the best technology of our ultrasonic sensing for the best sensor performance ever. It is designed for use with all aluminum, vertical LPG DOT cylinders up to 100 lbs. The sensor mounts with a retaining collar (included) that sticks to the tank bottom with pre-applied permanent adhesive; all preparation materials included. Read the sensor via Bluetooth with the free Mopeka Check APP on your smartphone or tablet; or Mopeka Check LED Display. Also compatible with Mopeka Wifi Bridge, allowing remote reading of sensor using APP. This package includes one Pro sensor, collar set with preinstalled adhesive, adhesive prep materials, and also includes four spacers that clip to foot ring to improve wireless range and provide adequate space as some aluminum cylinders have little to no space under tank.