Surface Tree Adapter Joint
Crossover from the standard riser joint connector to the connection at the bottom of the surface tree. NOTE Its bore configuration is consistent with the standard riser joint. This speciality joint is usually made up to the surface tree prior to installation.
Source: API RP 17G, Recommended Practice for Completion/Workover Risers, Second Edition, July 2006 (Reaffirmed April 2011). Global Standards