It is in in/hg, I had one in my crx when I first boosted it and it wraped the neddle so far around the 10, fast I thought I blew the line off of the wg, It turns out that I had to get a different gauge, I didnt know what boost I was running, went and bought A sunprow for cheep, from jcw. Watch out for that boost gauge, its better for a vac. than boost !!!!!!!