Can anyone tell me what size nut is on the fan clutch?

I don't have any wrenches that fit it (my metric set is lacking), and I am not using channel locks :P.

Thanks!

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06 CRD Limited. IMII, GDE TCM, Carter transfer pump, Upgraded oem primary, 2 micron secondary, 3 inch mandrel straight pipe.
Transgo shift kit, EHM, fcv butterfly removed, egr plated off. 19 3/8 solid flex fan, no electric fan, 10k lb aux trans cooler.
Frankenlift II, Mopar skids, allj's rails, 235/85 km2 on stock rims