I forget off the top of my head, there was someplace else discussing this. This is a question I found on the corsair forums and though it wasn't stated by the corsair employee on this thread it wasn't disputed either. Rpm's are a bit different and the bearings are a bit different. That's why the led version are cheaper, they use a sleeve bearing instead of a slightly nicer more durable hydraulic bearing used on the plain af/sp fans with the colored rings.