Hi Little nellie, the prop hub is 5/8" across outside to outside, center of hub is 3/8" and 5/16" thick -- this is on the 10" props. the 8" are gone. it is my understanding and I could be wrong, but I was told to use the 10" props with the 3s and the 8" with the 4s.
I'm using the 3s 11v 4000...