Revwheels.com says 40mm for the model X and speedanstyle.com says 42mm. Both are ok, but the 42mm would be slightly better. The Rotas are 40mm and I think the Velox are as well. Beware though that wheelmax doesn't sell real Velox wheels, they sell their own rip-offs. Can you tell I'm shopping for rims right now too?I like the Rev's a lot but I hear their offset is horrible...haven't been able to find anyone with facts though, just people guessing...not sure even what the offset is on the Rev's...they just look nice.