It means the hose has a fluorosilicone inner liner bonded inside the normal silicone construction. Standard silicone is excellent with coolant, air and water but swells and degrades in contact with petrol, diesel and oil. The fluorosilicone liner gives you hydrocarbon resistance on the inside while keeping silicone's heat resistance, flexibility and long life on the outside.

Any time fuel, oil or fuel vapour will touch the inside of the hose. That includes fuel lines, oil breathers and catch-can plumbing, oil cooler runs, and crankcase ventilation where oil mist is carried. If it is coolant, water or clean air, standard silicone is the cheaper and perfectly adequate choice. If you are unsure what is passing through the line, ask us before ordering.

Yes. The fluorosilicone liner is compatible with modern ethanol-blended petrol as well as diesel and oils, which is exactly the situation where an older plain silicone or rubber hose gets into trouble. Ethanol attacks unsuitable hose from the inside, so a line can look perfect externally while it is breaking down internally.

Internal diameters from 6mm up to 63mm - 21 sizes - in 20 lengths from 50mm to 950mm. Order by internal diameter to match the outside diameter of the pipe stubs you are joining. Short lengths suit joining two stubs; the longer options let you bridge a bigger gap or make a flexible section in a hard pipe run.

-60C to +180C. That is a slightly narrower range than plain silicone, which runs to +250C, and it is the trade-off you accept for the hydrocarbon resistance. It is still well beyond what rubber fuel hose can manage, and it covers engine bay temperatures comfortably in normal service.

A fluorosilicone inner lining, polyester braid reinforcement for pressure stability, and a durable silicone outer layer that resists heat, ozone and abrasion. It is built to SAE J20 R6, is available in 3 and 4 ply depending on diameter, and the smooth bore keeps flow efficient. The braid is what gives it the pressure rating and stops the bore ballooning.