Surly Fixxer
 

I just joined, actually in an attempt to find info on how to install my recently purchased Surly Fixxer, but wasn't able to find anything to answer my question. But, after dismantling my hub (a ritchey hub,) and discovering it absolutely wouldn't work, I returned it to the bike shop and ordered a new rear wheel. They clarified, which I couldn't find anywhere, or maybe was too dense or inexperienced to understand, that the hub needs to be a shimano branded hub, not just any old hub that accepts a shimano cassette. I thought this would save a few people from spending $80 on the thing to discover that there was a much better option for them. Cheers!

Jonathan

yep. says so right in the description:
Cassette hub converter. Converts any Shimano cassette hub except silent cluth and pre 1997 Dura Ace, to a fixed gear. Includes all hardware. Does not include cog or lockring but is stepped for a track lockring.