These tubes are made with expanded silicone sheaths that incorporate a fiberglass braid onto the inner surface.
The silicone sheath ensures thermal and mechanical insulation, while the fiberglass sheath favors the assembly that takes place, by fitting the insulating tube onto the tube (normally made of metal), containing the fluid at temperature.
The thickness of the expanded silicone guarantees thermal insulation and protection within certain limits against impacts. The application is therefore on all dangerously hot/cold or fragile tubes that could be accidentally touched or damaged, for example during plant maintenance operations.
They also provide good sound insulation.