well, let's try and use our reasoning abilities. the seller says a derailleur chain won't fit. if this is true it is 3/32". 3mm is also more than 3/32". did he ask someone if the chain would fit, or does he have a 3/32" chain laying around? if he has the chain, it should be obvious what size the ring is. is this really that complicated? it just seems odd that the seller doesn't really seem sure if it is 1/8 or 3/32. he's got a bunch of other chainrings for sale, and none of them specify 1/8 or 3/32. it just say's "it fits my 10 speed chain" or "it doesn't fit a derailleur chain." the price is right, but how can someone with so many parts know so little. are these stolen or something?