I have 904f2 and 906f2 both 15* with graphite shafts, I felt the 906 was for a better swing than mine.
But digging thru my clubs I found 904f2 15*, and a 906f4 15.5* steel shafts.
Whats the difference between 906f2 and f4, and is there such a thing as 904f4??