It's a Gas

Do you need to go through the hassle of filling the propane tank before your big cookout, or is there enough left to get you through? You can take your chances. Or you can buy an expensive valve gauge. Or you can put one of these magnetic strips on the tank, pour on hot water to activate it, and read the tank level just a few seconds later. It lasts for years because there's nothing to wear out, it won't fade in sunlight, and it's simple to move from tank to tank.