If you’re looking to swap out your full-sized humbucking pickups, you’re likely to encounter a handful of different terms relating to the spacing of the polepieces. The following explanations will help you determine which style of spacing you need depending on the pickup manufacturer and the type of guitar you have.
DiMarzio “Standard” humbuckers measure 1.90″ (48 mm) center-to-center from the first polepiece to the sixth. A Seymour Duncan standard humbucker string spacing measures just a touch wider, coming in at 1.930″ (49mm). Due to the minimal difference in the polepiece spread, DiMarzio and Seymour Duncan standard humbucking pickups are interchangeable in most non-tremolo-equipped guitars, though it’s wise to measure the string spacing to make sure a standard-sized pickup is the best fit.
To accommodate the slightly wider string spacing of a tremolo-equipped guitar, pickup manufacturers crafted pickups designed to improve the alignment between the strings and the polepieces. DiMarzio’s “F-spacing” humbuckers measure 2.01″ (51 mm) from center-to-center on the outside polepieces. Similarly, Seymour Duncan Trembuckers measure 2.070″ (52.6mm). Again, a minimal difference between the two brands, and either will work in most tremolo-equipped instruments.
The rule of thumb is that if the string spacing is less than two inches or 50mm, a standard humbucker is the right choice. For string spacings larger than two inches or 50mm, step up to an F-spaced or Trembucker pickup size. Due to the magnetic field created by the polepieces, it’s not absolutely necessary for the strings to pass exactly over the center of the polepieces. However, it’s a good idea to keep the E strings from sitting completely outside of the outer polepieces, as the reduced magnetic force could have negative impact on your tone.