Singleworks CrMo cogs. I just did a search and didn't find a discussion on these gems. They are similar to Surly but a little cheaper ($18) and a little lighter (20T SW-66gms; 19TSurly-69grams) and the base is a little wider (4.4mm-Surly; 4.5mm SW). I just picked it up and am installing it as we speck. Anyone have any experience with these.