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GotGrit.com has Silicone Carbide down to 60 grit and sells as little as a ¼ pound.

You can buy 60-500 for under $15. A steel cookie sheet and 60 grit will get you flat.

There are some brown coticules, supposed to be harder and fine finishers, there is one for sale on French ebay, now, for over 200.

Though the slurry looks like Kita slurry.

What does it finish...