Product review (1 stars): Vital information missing to intelligently order these fan blade arms
It is absolutely essential to know what the spacing of the attachment holes is at the motor hub.  Without that bit of data, one is just shooting in the dark.  There are several different spaceings depending on the manufacturer.  It is rare to locate this vital bit of information from most mail order suppliers.  My luck has been much better when ordering from stores that specialize in fan parts.  The brackets are fine if you get lucky and get the proper spacing.  It is NOT standard to all fans.