Minimum diameter that allows for the passage of the drift.
Source: API Standard 2RD, Dynamic Risers for Floating Production Systems, Second Edition, September 2013. Global Standards
Minimum inside diameter (ID) of a packer, expressed as the OD of the drift bar utilized during assembly inspection, as outlined in 7.4.11.
Source: API SPEC 11D1, Packers and Bridge Plugs, Upstream Segment, Second Edition, July 2009. Global Standards