Wikipedia
Everflex is a British fabric used as a roof covering on cars, and is a type of vinyl roof
Everflex is used on both hardtops and convertibles.
Its usage was popular from the 1960s to the 1980s on luxury cars. Though its popularity has greatly decreased for new vehicles, it is still manufactured for restorers. The material is similar to the vinyl used on most vehicles, but is more durable and more expensive. On hardtop vehicles, fabric is placed below the Everflex material to add weight and body, often making the car look more like a genuine convertible. On older vehicles, a fabric called "Union Cloth" was used, but it quickly deteriorates; trapping water and damaging the Everflex material and roof. The Everflex is then glued down and can be screwed in around doors and windows. Three notable car companies that use Everflex material are Rolls-Royce, Bentley Motors Limited and Jaguar Cars. The feature was most popular on the Rolls-Royce Silver Shadow in the early 1970s.