Bora 501057 Fine/Coarse Combination Sharpening Stone, Aluminum Oxide The BORA 6-Inch aluminum oxide sharpening stone is a 2 sided stone with one coarse grit and one fine grit side. Ideal size for bench work 2 sided - one side is coarse 150 grit the other side fine 240 grit. Intended for sharpening all types of tools and knives 1 year warranty Measures 6" x 2" x 1"