The 12K stone I have is this one from Shapton https://www.amazon.com/Shapton-M5-12.../dp/B002LW76XY

I also have some 6K stone (https://www.amazon.com/gp/product/B00MD4K3QM), and 1K by the same company that I use to maintain my kitchen knives. I always thought that anything below 10K is too low for a razor.