KGS Diamond whetstone PRO is a precision diamond sharpening tool. Well suited for very fast sharpening or deburring any hard, brittle material. No need for conventional sharpening stones any more, KGS Diamond sharpening stones work much faster and have an incredible long life! If you use the whetstones on a daily basis and maintain them properly, the diamond will likely last for a few years. For those that use them less frequently, it's likely the stone will last from 10 to 20 years! Diamond sharpening stones can be used dry or wet, but wet is recommended. When using them wet, use water (not oil).