I needed some cogs for my first fixed conversion and found some at KB cylce werks. They were originally $9.99, but I see they raised the price to $12.99. I actually bought three for $25.
They just arrived and I'd like to report on the cogs. TEETH:They are nicely machined, CNC cogs. THREADS; are fine - I tried them out on a new hub and they and look and feel very good. Cogs are just under 8mm and line up perfectly to my hub's 42mm chainline. I'll use a bit of anti-seize when assembling, just to be safe. HARDNESS: I'm a tool and die make by trade and without a Rockwell tester, I'd say that they are about 55-58 Rc. FINISH Matt black with lettering. Not flashy, but utilitarian.
They are more than I expected for the price and I think they'll do just fine for a fixed/ss.