Tools4Boards Hone Diamond Duo 400 Grit One Side/600 Grit Opposite Side Stone, Yellow/White Premium Swiss-made diamond fabric - 400 Grit on one side and 600 Grit on the opposite side Exceptionally flat precision milled stainless steel backer Unlike plastic or aluminum backers the 5/32" (4mm) thick Hone stainless backer will not flex and roll over dulling the cutting surface of the edge 400 Grit side is perfect for all round maintenance and polishing - typically used as the third stone in progression from coarse to fine grit 600 Grit side perfect for final polishing after edge bevel and sharpness have been established