ISO 10423:2009 specifies requirements and gives recommendations for the performance, dimensional and functional interchangeability, design, materials, testing, inspection, welding, marking, handling, storing, shipment, purchasing, repair and remanufacture of wellhead and christmas tree equipment for use in the petroleum and natural gas industries.

ISO 10423:2009 does not apply to field use, field testing or field repair of wellhead and christmas tree equipment.

ISO 10423:2009 is applicable to specific types of wellhead equipment, connectors and fittings; casing and tubing hangers; valves and chokes; loose connectors [flanged, threaded, other end connectors (OEC), and welded]; and other equipment, such as actuators, clamp hubs, pressure boundary penetrations, ring gaskets, running and testing tools and wear bushings.

The nomenclature is defined and most physical dimensions are given in USC as well as metric units.

ISO 10423:2009 defines service conditions, in terms of pressure, temperature and material class for the well-bore constituents, and operating conditions.

ISO 10423:2009 establishes requirements for five product specification levels, PSL 1, 2, 3, 3G and 4. These five PSL designations define different levels of technical quality requirements. Guidelines (not requirements) are provided for selecting an acceptable PSL.