This product can safely and accurately measure the gas capacity, according to the gas temperature test, measuring the temperature range of -10 C~ 120 C. actually show you when you are low on gas, before you run out! Works while you are using the BBQ Save money by using more gas from each cylinder Safe & accurate Reusable Works on LPG (propane) & butane cylinders Magnetic backing allows for easy reuse on exchange bottles Comes with instruction Instructions: 1.Place your Gas Level Indicator on a clean area on the lower half of the cylinder. 2.Turn on the gas and wait 10 minutes before you can read your Indicator. 3.In the winter the bar on the left be active, and in the summer the bar on the right be active. Colour:black Material:pet Package Contents: 3 x Magnetic Gas Cylinder Tool Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.