DiMarzio DP153FB Fred Humbucker Pickup F Spacing Black - F-spaced pickups measure 2.01" (51 mm) center-to-center from the first polepiece to the sixth. Standard-spaced pickups measure 1.90" (48 mm). Although some players believe that F-spaced pickups are only for the bridge position of tremolo bridge guitars, many guitars with fixed bridges (including post-1998 Gibson® and Epiphone® Les Paul®, SG® and semi-hollow guitars) should have F-spaced pickups in the bridge position. Most tremolo equipped guitars that have a nut width of 1-11/16” (43mm) or more should also use an F-spaced pickup in the neck position. If you’re replacing a bridge-position pickup and you're not sure what your string-spacing is, it's usually better to get an F-spaced model. It is not necessary for the strings to pass exactly over the center of the polepieces for best performance, but it is wise to avoid a situation where the E strings are sitting completely outside of the outer polepieces.