Was it mentioned that some Shapton Glass exist in two versions, HR and HC? I have the HR 1-16k glass stones (white color), which I love. I also have 4 and 8k in HC (grey color, I believe a 6 exists too). I get a better polish with the 8k HC than I do with the 16k HR....go figure (anyone else have same experience?). You can see and read about the HR (and HC) glass stones at Dictum and Aftramestokyo.