Precision Bass®, or P Bass®, pickups come in a wide variety of stylings. Most manufacturers make different windings with different goals in mind. Some models shoot for true old school tone, utilizing the same materials and windings that had been used in early bass production models decades ago. Thankfully, the overwhelming majority of P Bass® pickups come in two shapes, and those shapes are quite identifiable. Either you need the ’51 P or the currently more common P. Not much measuring to do here :)
A word about Tone: We have categorized the P Bass® pickups into 4 different tone voices: Vintage Era Correct, New Vintage, Modern, and High Output. For some models, this is a bit tricky to pin down - often a pickup can be designed to do two things. An example of this would be a pickup that is aiming to have a vintage tone but is wound to be higher output. We can’t exactly call this Era Correct Vintage, but can fit it into New Vintage and High Output. Some pickups fall into a couple categories.