inch thick. Zirgo list this fan as their 4000 cfm straight blade fan, don't know the pn# off hand. I never said it flows 4000 cfm but even if it flows less it still gets the job done. I don' t care if it does n't out flow a fan clutch & I am not encouraging other to switch to a e-fan I am one of 99.9% who has a e-fan set up & has had positive experiences w/ it.