Are the CFMs on PC fans legit?

Ive got two 4.5in PC fans that I use for very small box, they say they move 100 CFM each but I've heard PC fans don't work the same as regular inline fans. Does anyone know whether or not 100 CFM is a realistic claim for these fans?

It all depends on the manufacturer. Some ratings sare dead on, other are complete BS. Check out reviews on newegg, people usually say if it doesnt move as much air as it says.