25 microns. The Dia-Sharp Sharpener D2 Fine has a tapered, tempered spring steel front end that forms an extended easy access tip; ideal for honing in tight places eg secateur or lopper blades. The Dia-Sharp Sharpener D2 Fine uses 600 grit Monocrystalline diamonds securely bonded in nickel, and then electroplated onto a solid stainless steel plate. The uninterrupted diamond sharpening surface makes a Dia-Sharp sharpener ideal for putting a razor edge on knives, axes and loppers. Unlike a conventional knife sharpener, a Dia-Sharp Sharpener stays perfectly flat for precise sharpening. You won't develop grooves or hollows in the blade and the blade never needs dressing. Easily cleaned with a standard office rubber eraser.