SAE J531_201511 Standard includes dimensional specifications for square hexagon inside types of pipe, filler, and drain plugs commonly used in automotive and related industrial applications.
Figure 1A square inside head pipe plugs 130109A
Figure 1B square inside head filler and drain plugs 130109B
Figure 1C square inside head pipe plugs 130109C
Figure 1D square inside head filler and drain plugs 130109D
Table 2 - Dimensions of square and hexagon inside head pipe, filler, and drain plugs
(Figures 1A TO 1D)