Quite a specific screw to be honest - i cant think I've seen them being used for anything else apart from mounting Filtertron pickups.

They're quite a strange screw in their own right too, very long (at 1.75"/45mm total length) with the threaded section being less then half the length of the shank to allow avoid binding within the pickup itself, and differing from most pickup mounting screws/bolts, because they're slot headed.

Also available in a shorter 1.23"/31mm version

Quantity - 4
Thread - #3 (2.3mm Diameter)
Thread Length - 21mm
Shank Length - 43mm
Total Length - 45mm

Head diameter - 4.5mm
Head Style - Counter sunk domed slot head
Material - Mild Steel