W10 Double sided combination diamond whetstones will not break chip crack hollow or groove These ultra precision whetstones are lightweight and have a totally rigid construction Use water for lubrication no oil smell or mess and can hone ALL hard materials carbide steel the grits are denoted by a dual coloured circle which is set into one end Black Extra Coarse Grade 220 60 micron Blue Coarse Grade 325 45 micron Red Fine Grade 600 25 micron Green Extra Fine Grade 1200 9 micron