The spark plug standard is M14S × 1.25. See JISB8031.
Since OH4 falls into the category of OH4 accuracy, A-SFT's M14×1.25 (STD+1) (= OH4) corresponds to it.
M10S×1→OH3
M12S×1.25→OH4
M14S×1.25→OH4
* In 1995, the standards for spark plugs for internal combustion engines were revised.