When our supplier sent us a sample of these I didn't get too excited because they look like a bit of a boring tool but after trying them on a blunt old chisel I was impressed at how easy it was to get get such a sharp edge.
All I had to do was start with the coarse grade, then move to the fine and finish with the extra fine grade. My chisel was so sharp I could shave with it!
They can be used dry but work better and last longer when used wet. The water provides lubrication and flushes away the filings to give a cleaner edge. Just put the diamond stone into a shallow dish (rectangular takeaways lids work well) and cover the stone with water by a few mm. When done rinse them off and dry with a soft cloth.
Each sharpening pad has three layers of diamond coating bonded to the steel substrate then mounted to a rigid plastic frame.
TCT router bits
Carbide steels etc
Coarse 200 grit yellow stone 150 x 50mm
Fine 300 grit red stone 150 x 50mm
Extra fine 400 grit green stone 150 x 50mm
Rinse and dry after use (otherwise the blade filings will rust onto the surface).