Allen Key size for wheel mounting screws

I have the A4WD autonomous kit which thoughtfully included a small allen key for tightening the wheel hubs onto the motors, however, the wheels themselves are held on by a long screw that uses a larger allen key, I have 2 key sets, both metric and SAE, but none of them fit…can you tell me what the size of key that screw takes?

Thanks…

I believe it’s SAE 5/32.