Bikewagon has these, says they are 94 mm BCD. Sheldon Brown says the MC30 and MC31 arms are 95 mm BCD. To me it looks like they are neither, and only have the 58 mm inner ring holes. Were these cranks made to take just a single inner ring? If so, do they have different model numbers for single and triple? Is the listing another case of seller using a stock photo that isn't the correct one? I asked Bikewagon to check stock and see what the actual part looked like, but they replied that the arms are coming from an outside supplier and they didn't have one to check. Is Sheldon's measurement correct? If so, I'm guessing the chances of finding rings to fit are slim.
https://www.ebay.com/itm/Shimano-STX...frcectupt=true