TD40 BLE - LR 4&'; to 18&'; Tall - Work with All Non-Pressurized FluidsSonar Tank Monitoring Solutions are the most reliable and accurate way to measure Propane, Butane, LPG, water, beverages, and other liquid volumes in both pressurized and non-pressurized tanks. The TD40 can work on tanks up to 16 high and communicate via BLE (Long Range Bluetooth)*Installation will require a threaded 2" port, or you must cut a hole 2" (50.8mm) in diameter in the top of the tank at the chosen location.Features: The sensors work on Boosted Bluetooth. The average sensor&';s battery life is 5 years*, so you don&';t need to worry about continually changing the battery, and they&';re replaceable. The latest in cloud-based software with our partner Amazon Web Services. The sensors are so accurate that they can read down to a .01 of an inch. The TD200 sensor is classified Class 1 Div 1 Easily select the liquid commodity you are measuring from the dropdown list in the "Tank Check" or "Co-Pilot" App 3-Year Warranty from the original date of purchase by the customer