This is the smallest knife available on the conservation market, with a .9mm width. The M2 steel blade fits into the supplied standard mechanical pencil handle, so it can be fully retracted when not in use. The blade can be extended to about 20mm to reach into recessed areas. It has a double bevel, and can be used for fills, working under magnification, extremely delicate cutting, or anywhere you need to make a precise cut. Great for complex shapes for tissue fills and it can cut up to cover weight paper. The M2 tool steel blade (Rc 65) can be resharpened and stropped. In case you are not familiar with mechanical pencils, just depress the button on the end and hold it down to retract the blade. Just don't mistake it for a pencil!