Mopeka TD40 BLE - LR 4' to 18' Tall - Work w/All Non-Pressurized Fluids [M2012003]TD40 BLE LR 4' to 18' Tall Work with All Non Pressurized Fluids Sonar 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