The assembly of the pair of extruders requires 3 x M3 16mm screws per extruder, but the fastenings pack only contains 4 M3 16mm screws. The label on the bag says it contains 4, but as 6 are needed maybe everyone else is 2 screws short as well?
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You may be able to source the extra screws locally quicker, and of course if you're using your own extruders you won't need them.