This fits in any pants or apron pocket. A handy, lightweight natural sharpening stone based on quartz carbonate that is quickly ready for use at any time. The natural stone is quarried in Lombardy for the French knife specialist. To re-sharpen, run the blade along the grindstone at an angle of 22 to 25° and repeat this process three or four times from both sides. The only necessary preparation: the stone must be watered before use. For all knives with a smooth blade.