Review on GrillPro 00030 Magnetic Gas Level Indicator: Effortlessly Monitor Your Propane Tank Levels by Phillip Brown

If your tank has plastic shrink tubing, it won't stick. The magnet is not very strong. You can only read the bottom 4 inches of the straight side of the tank. I think that's all it takes. The curved bottom has a gas reserve when the gauge shows the tank is empty. My previous grill had a spring scale that worked pretty well, but the new grill removed that useful feature. The directions aren't big, but if you look at the indicator, you can understand where the level is. Only read if you are actually using propane from a tank. When the tank is stopped there is no display. Not sure if this works in very cold weather.