Dimension B is minimum length of perfect thread. The length of useful thread (B plus threads with fully formed roots and flat crests) shall not be less than L2 (effective length of external thread) required by American National Standard for Pipe Threads (ANSI/ASME B1.20.1). See Section 6.3.
Class 2000 and DN6 Class 6000 couplings, half couplings, and caps are not included in ASME B16.11.
