A set of 6 pole screws. These screws are used to charge the strings of the instrument by transferring magnetism from the magnet that sits under the pickup bobbin to the screw head, which in turn charges the string.
These screws screw directly into the metal spacer of the pickup and are anchored there, unlike on a mini humbucker, where the pole screws screw into the baseplate. M3 x 18.5mm. Sold in sets of 6.