Coghlans Butterfly Shape Knife Sharpener Sharpens stainless steel or carbon steel knives in seconds. Weighs less than 1/2 oz. (14 g) Diamond ground tungsten carbide bits. Maintaining the quality of your survival knife begins with proper use, but also proper sharpening. You can damage your blade by not properly sharpening your knife and this pocket knife sharpener by Coghlans allows you to do just that. Don't destroy your survival gear, it may save your life.