The Gaslow Butane 21.8LH 500 Adaptor Gauge is designed to fit the 4.5kg Butane cylinder.
it provides a visual warning of low gas levels, with the Green/Yellow/Red display. Secondly it operates as a quick and easy leak detector. It can also be used with the relevant adaptors to fit 7kg, 15kg & Camping Gaz cylinders.
Some of the images show the gauge fitted to a cylinder and regulator, these are not included.