CBN stands for CUBIC BORON NITRIDE and is a ceramic grain with an equivalent hardness to diamond.
The major advantage of this material over diamond is that it can also be used for grinding HSS steel (the material out of which most turning tools are made), without using a coolant and without the risk of heating the steel.
You don't need to put pressure on the chisel to sharpen it, the weight of the chisel itself is usually sufficient.
These OptiGrind stones remove material very quickly but still give a fine result.
The CBN covers the total width and a part (15 mm) of the side.
Optimal speed: 1700 - 3000 rpm
Grit: (B91) P150