Here you will find all the springs that you might need to fully mount a pickup.
Stratocaster Springs : Length 13mm / Base 7.2mm / Top 5.3mm
Humbucker Springs: Length 28mm / Base 4.6mm / Top 4.6mm
Telecaster Springs: Length 15mm / Base 5.2mm / Top 5.2mm
P & J Bass Springs: Length 18mm / Base 7mm / Top 5mm