3/4 inch, seems to be much heavier than the stuff i see at hdepo. Just been ding some quick reading, this is not the thin wall emt. I picked up about 20 6-foot sections. I know it has grading labels, will check. But good point about it not being designed for heavy load bearing! I just scored 20feet of the struts used to support the conduit. Am now looking at one of the weld-less builds in other threads.