Chainring spacers - all same ID?

[NHAero]

This fiddling never ends :-)
I swapped out the North Shore Billet 104/64 spider for the SRAM 120/80 spider to go from 40 to 42 large chainring. Now I get FD cage rub, and I see the chainrings are spaced more widely on the SRAM. I see Origin8 sells a pack of 20 0.6mm spacers, seems like a good idea, since you could potentially stack them. I can't find anywhere a spec that tells what the ID of the spacer is, and chainring bolt ODs vary, and these require a 10mm ID on the spacer.
Anyone know this arcane bit of info? Thanks

[Mark McM]

I don't know about the Origin8 chainring spacers, but I do know that the Wheels Manufacturing chainring spacers have a 10mm internal diameter, for use with standard double and single chainring bolts, and which will also work with the 10mm bolt on SRAM's 120mm BCD chainrings.