Man made bench stones come in a variety of shapes & sizes and are available in a range of grit sizes: coarse (80-100 grit), medium (150-220 grit), and fine (280-320 grit). Benchstones are durable, wear slowly, and retain their flatness significantly longer than waterstones. 

Because sharpening is usually done in stages, first repairing an edge with a coarse grit stone and then perfecting the edge with a fine grit stone, many people choose to buy a combination stone giving better value for money, utilising a coarse grit on one side and a fine grit on the other side.