F spaced - originally means "Fender spaced" ... yung string space ng fenders are bigger than that of Gibson bridges(regular Dimarzios)...
So if you have a strat type or super strat type guitar(yung naka floyd rose trem of the likes) get the F-Spaced ones.
pag seymour duncan pups naman, they call their F Spaced pups yata as trembuckers...