These are for airplanes that use 100 Octane Only fuel. These Fuel Placards have a Heavy Lamination to protect it from fuel and scratches during refueling. There are 2 Fuel Placards in one and sold as 2 pairs. 1 Pair small for cap & 1 Pair Large. The outer Fuel Placard has a 3 3/8 center The inside Fuel Placard can be used on the cap.