API Spec 6A is an International Standard that 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.
This International Standard does not apply to field use, field testing or
field repair of wellhead and christmas tree equipment.
API Spec 6A is a modified national adoption of ISO 10423, 4th Edition :
Petroleum and Natural Gas Industries - Drilling and Production Equipment -
Wellhead and Christmas Tree Equipment