#1
This may be a stupid question, but can any brand of pickup cover, fit onto an other brand of pickup?

ie: A gibson pickup cover, put on a fender enforcer humbucker?
"The road ahead is lined with broken dreams, so walk, just walk on by..."
#2
as long as its the same type of cover for the pickup (humbucker sized to humbucker, etc)

you cant jsut screw them on and call it a day though, tehre will always be space inbetween the pickup and the cover, this will cause constant feedback, so you need to wax pot them. But ya, as long as they fit on top of the pickup, and fit into the pickup slot, then youre good to install them.
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Gibson Les Paul Studio w/dirtyfingers pickups
Gibson Joan Jett Melody Maker
VOX ac30 head
Marshall 1960 4x12 cab
Fender Hot Rod Deville
#3
i jsut recently found out that fender single coil pickup covers will NOT fit over squier ones. now that pissed me off. well they fit over it ok...just that the pole pieces do not line up properly.