This part of ISO 4039 specifies the essential dimensions and material requirements for metallic and thermoplastic pipes, male fittings and tapped holes with a conical sealing surface, of the metric series, used in pneumatic braking systems on road vehicles using compressed air at a pressure below 2 MPa (20 bar). Annex A gives, for information, an indication as to the relationship between this part of ISO 4039 and ISO 6149, and a recommendation on how to indicate conformity with this part of ISO 4039