Swivels for rigs

Hi just wondering. Is size 6 sakuma rolling swivels a good choice for main line to rig and size 3 for the snoods?

What about the diamond swivels?
Whats the difference in the sizes for swivels, i think 6 is big and 6/0 is small the other way round from hooks. Am i right??

Any help appreciated.

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