I never heard if Ofmega cranks have a different size threaded hole compared with other cranks, but it does happen, at least with Stronglight cranks, which had bigger threaded holes on their older (mostly pre-80's) models. Many Stronglight cranks are damaged by their owners when they try to remove them using the smaller more universal sized removal tool..... I'm wondering if it's the same case with some Ofmega cranks.