I wrote:
Is this auction a joke?
It's patently obvious that that cog is anything but new and, in fact, rusted to a ridiculous extreme.

Seller's Reply:
Hi, Thanks for your input. My photo is not very good, but the cog is black anodized, and the surface is not a consistent colour. It is a new cog, just shipped about a month ago from a major U.S. distributor. All the other cogs i got at the same time were silver, but this the largest available from this source, is black. Perhaps you can see the threads on the inside show no signs of use. Nor do the teeth of the cogs. Please review my feedback if you doubt my integrity. Of course you are under no obligations to bid. But thanks for bringing to my attention exactly how poor the photo is when show on eBay. I will try to take another photo tomorrow. Perhaps if i use a different background i can get a better photo. Do you have any suggestions in that regard? If you are interested in this 18 T cog please let me know & i will try to get you a better photo.
Again Thanks for your input.