Every day...

....Ya' learn, ( something new) . Inside roller dia. of stock 2013 wr250r 520 o ring chain is .0200 or 2hundred thousands.
Left laying around the bike shed are/were assorted links of DID VM, and EK RXO 520 -.0210" roller I.D.
PIN dia. for Masters for VM,VX2 and RXO are .o205"
Don't try, It W'ont work! Don't ask how I Know/   
I ordered a new chain, Life is complicated enough without having different roller and pin sizes for the same size chain floating around in the hell hole.
Jeff

Yessirree, one brand's 520 chain won't necessarily have the same diameter pins as another brand's 520 chain.

.0200 = twenty thousandths.

I'm trying to imagine what part of the chain is .02 inches.

Thanks for the help!
  You can get the o ring down to 20 thousands- just keep tightening  the calipers.   
 520 pin diameters are  in the .2 range,   My mistake
    Thanks  again