The Glow-worm packing ring is designed for use in the heat exchanger of CXI, Easicom, Energy, Energy 7, Flexicom, Home, HXI, Ultimate, Ultracom, Ultracom2, Ultrapower, Ultimate 3, Energy 2, Essential, Sustain, Ultimate 2, Betacom, British Gas, Eden, SXI and Xtramax units. O-rings, gaskets and washers are used in many different areas of the boiler to join parts to pipework. Heat exchangers and gas valves among other sections require these parts to prevent gas and water leaks.