8" x 3" Diamond Combination Sharpening Stone 300/1000 Grit Diamond grindstone, coarse grinding and fine grinding combine, first coarsely grind for polishing Place the knife on the diamond surface and keep an angle for about 30°. Move back and forward for several times, then change the other side of the knife and repeat the same process.Start with 300# first and repeat on the 1000# side.