It is a fuel gas tank level indicator.
This product can safely and accurately measure gas capacity.
According to the gas temperature test, the measured temperature range is -10°C~ 120°C.
Its Magnetic backing allows for easy reuse on exchange bottles.
It can help you save money by using more gas from each cylinder.
It works on LPG (propane) & butane cylinders, safe and accurate.
It will actually show you when you are low on gas, before you run out.