Monument Gas Test Gauge is made from tough plastic. Used both for testing pipework installations with air for leaks before the introduction of gas and for checking and setting correct gas pressures on domestic and commercial appliances. Extruded cover slides off and may be clipped over the base for standing the tool vertically during use. Hanging tab permits vertical hanging from suitable protrusions. Marked in millibars, the scale adjusts for zeroing water level. Plastic U Tube. Made in Britain.