Usually, there are two types of electrode, Ignition electrodes and flame sensing electrodes. The Ignition electrode is responsible for making the spark that starts off combustion. The flame sensing electrodes are responsible for ensuring there is a flame present in the burner. This is an important task that ensures the boiler doesn't keep supplying gas while no flame is present.
Fits certain boilers
Technical specification
Waist Sizeah43cd3gsToilet Cistern CapacityFTW--Manufacturer Model No500680Brand NameHalstead