管用ねじ　6a　8a　10a　15a　20a　25a　32a　40a | オーエスジー

10A may be written in the place of the screw symbol for the pipe in the drawing.

This 10A refers to 3/8 of the size of the pipe screw.

○○A is a size expression in the piping standard.

The expression and combination in "inch size " like a unified thread are decided.