Back-up rings have no intended sealing function. Instead, as their name indicates, they are protective and supporting elements made from extrusion-resistant materials which generally have a rectangular cross-section. They are installed in a groove together with an elastomer sealing element, preferably with a corresponding O-ring in static applications.
Motorists need incentives to buy EVs - report
Frankly a £1000 cut on VAT will make little difference if buyers cannot be tempted by the completely unsustainable level of discounting being offered...