This gasket seals the connection between the hob surface and the burner support. This gasket has a diameter of 122mm and is for the large burner on your hob.
Rust or burnt on grease and grime can make your pan stands an eyesore on your cooker. Luckily there are replacements to have it looking brand new again. This pan support is for the left hand side of the hob top as you look at the appliance.