Thinner than a credit card and 64 x 100mm, the GLI's magnetic backing means it can be attached to the outside of the cylinder. We use a high quality magnet backing, that with careful use should last the life of the indicator. The GLI is designed as a warning device which shows when the gas bottle is running out. · A product of Good Life Innovations.com· Made in the UK· By the people who make the World No. 1 selling Gas display Magnetic Backing (Guaranteed for the life of the indicator)· Safe and Dependable· Use today.....every day· Re-use again and again. Comes with full instructions and to understand the science of how it works. The unit is designed ideally to work in ambient conditions between 14 to 40°C. Our new stock of rectangular indicators are made in the UK from manufacturers who invented the Gas Level Indicator Latest liquid crystal technology. We do NOT supply rectangular indicators from Asia. * Makes a great all year round gift! *Please see our Store for details Please note: We care about the environment and wherever possible use recycled packaging. Please Note: We only sell Gas Level Indicators and thermometers made in the USA and UK by the Global Leader in colour change technology. All our thermometers are made to ISO World Standards and Procedures and only the latest technology of Liquid Crystal is used.Some of our materials are even used by NASA on the Space Shuttle. We would like to highlight that these Gas Level Indicators are not suitable for the smaller gas bottles below 5kg and below. They should not be place over a weld. Please contact us for an alternative if using smaller bottles. Another good idea from Colour Changing Products This item is not suitable for gas canisters on vehicles.