Ideal parts are based around the diverter valve section. The diverter valve is a directional water device that only appears in combi boilers. It allows the hot water to be sent to the heating system or to the domestic hot water system. This feature is what separates a normal boiler from a combi boiler due to the fact that the boiler can provide hot water and heating without the need for a cylinder. This is the Ideal 173967 Diverter Valve Cartridge Kit, specifically for use prior to XF models and compatible with Honeywell VJ6012 (Red Topped Diverter Head) systems. It is a genuine Ideal spare part.