This European Standard specifies basic dimensions of cylinder valves (manufactured in accordance with EN 13152 and EN 13153) and connectors (including regulators) to enable them to be connected together. This European Standard lists connections where it may be possible to connect together, but which when connected may not be sound or secure in some operating conditions or orientations. This European Standard also recommends tightening torques for the attachment of screwed metal-to-metal connections. This European Standard contains the drawings, which describe direct cylinder valve connections in the following standards: - EN 12864, - EN 13785, and - EN 13786. Quality assurance systems, production testing and particularly certificates of conformity are not covered in this standard. This European Standard excludes connections for automotive vehicles covered by UN/ECE Regulation 67 and EN 13760 and excludes connections for cartridges.