New now with 4 strong neodyn magnets in a matter of seconds you can see the gas fill levels in commercially available 5 11 and 33 kg propane bottles its the perfect level gauge for propane levels when camping barbecuing crafting or for outdoor heaters application simply place the gas level vertically at various points on the tank using the 4 magnets on the back depending on the gas level of the vessel the signal light changes from red to green and vice versa includes lithium battery