Right, but the ovoid rings seem more of an on-road thing. Sheldon used to talk about using them for fixed gear bikes, for example.

Never warmed up to them for either mountain or road bikes myself, though. They always seemed too lumpy, like they wouldn't spin properly.

I've no idea why Shimano ever put them on mountain bikes. They're kind of a waste in the tight single-track conditions present here in southeastern PA.