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I picked up an only great eagle model but it didn't come with a base, just the flying stand. Are they supposed to be 40x40mm or 50x50mm bases
40mm x 40mm. Same as other 3 wound monsters.
I am right 94% of the time, why worry about the other 3%.
GW posted a nice list with base sizes an unit strength, might be helpfull forthe rest of yer army
a bit outdated but stil usefull to some.
Warchief Diggah o da Bloodmoon Squiggahs