This Standard specifies screwed type steel pipe fittings (hereafter referred to as "fittings") used for ordinary piping for water, oil, steam, air, gas, etc.
JIS B 2302:2013 Referenced Document
ISO 6708 Pipework components - Definition and selection of DN (nominal size)
JIS B 0151 Iron and steel pipe fittings -- Vocabulary*, 2018-03-20 Update