This Gas Industry Standard (GIS) specifies requirements for inflatable, self-centring bag stoppers. These bag stoppers are for use with the low pressure range of flow stopping equipment of the supported bag type for use on cast iron, ductile iron, steel and polyethylene (PE) pipes of a size up to and including 300 mm (12 in) nominal inside diameter, carrying natural or manufactured gas. Additional requirements are given for oil-resistant bags.