The Mopeka Propane Standard Sensor gives you peace of mind while on the road, tracking your propane tank levels in real time. Easy to install, the sensor magnetically mounts to the bottom of your LP tank and communicates via Bluetooth, giving you updates every five seconds. With the Mopeka Check app (or RV Whisper app), you can easily monitor your tank levels and get updates every five seconds. No more guessing how much propane you have left in your tank - the Mopeka Propane Sensor keeps you informed and in control! The Mopeka comes with the following: * 2 Mopeka Tank Check sensors * 8 Tank Check spacers * Small tube of dielectric grease * Instruction manual * TechnoRV Learning Series