Both convex and concave shapes provide an ideal surface for sharpening those chisels, gouges and other curved surfaces that a straight, flat surface can`t seem to touch. The curved surface ranges from 1" to 1/16" for a variety of edges to be sharpened. This unique sharpener comes with a 10" x 4" non-skid mat for a secure work surface. The mat can also be used as a base for any 10" or less whetstone. Use dry or with water as a lubricant. Available in two diamond grits – fine and extra-fine.