[1]This product can safely and accurately measure the gas capacity, according to the gas temperature test, measuring the temperature range of -10 ~ 120 . Will actually show you when you are low on gas, before you run out! [2]Save money by using more gas from each cylinder [3]Safe & Accurate & Reusable [4]Works on (propane) & butane cylinders [5]Magnetic backing allows for easy reuse on exchange bottles Please note: the physical slightly color difference or difference, number or different, but does not affect the use, please do not mind, thank you! 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 on the left will be active, and in the summer the on the right will be active. Colour:Photo Color Material:pet+soft magnetic Package Contents: 5 x Gas Level Indicator 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.