Measure your with this, simply attach it to your for tank cylinder with this and it will show you how much is left in your for tank Works while you are using the BBQ Save money by using more from each cylinder Safe, accurate Works on : PET Plastic+ Liquid Crystal + Soft Size: 10 * 6.2cm * 0.1cm / 3.94 " * 2.44 " * 0.04 This product can safely and accurately measure the capacity, according to the temperature, measuring the temperature range of 10 C~ 120 C.Will actually show you when you are low on, before you run out, Manufacturer: Oxxggkao