Bolt size help?

[JustBeginning0124]

I’m wondering if anybody could tell me the what kind of bolts are used to bolt the chain sprocket to the back wheel hub? I don’t know the exact size for them, and I’m not good at measuring bolt sizes, they are small I’d say probably an inch at most in the threads, 3/16 allen head it’s a 6 hole on I’m guessing either the smallest mini bike or the second smallest frame definitely not a full size

 

[Denny]

Usually 5/16”