ISO 23933:2006 specifies requirements for aramid reinforced lightweight polytetrafluoroethylene (PTFE) hose assemblies for use in aircraft hydraulic, oil and fuel systems at temperatures between -55 °C and 135 °C (-65 °F and 275 °F) and at a nominal pressure of 21 000 kPa (210 bar) (3 046 psi) or 20 684 kPa (3 000 psi). The hose assemblies are also suitable for use within the same temperature and pressure limitations in aircraft pneumatic systems where some gaseous diffusion through the wall of the PTFE liner may be tolerated.