The Spyderco 305M1 ceramic pocket sharpening stone medium grit is, because of its compact size, perfect to sharpen knives while on the road. Because of the medium grain size sharpening is quick and doesn't require water. As a result you can easily pop your stone in your bag or pocket after use!
The sharpening stone is made from aluminium oxide. The hardness is 9.2 on the scale of Mohs. That is almost as hard as diamond to make sure that sharpening rock-solid types of metal and even most carbides is very easy.
The Spyderco 305M1 is dishwasher proof and can handle sterilisation in an autoclave. It is therefore also perfect to sharpen, for instance, dental tools or other medical equipment.
There is also a larger version of this sharpening stone.
If the ceramic sharpening stone is clearly affected by metal deposits you can clean it with water, an abrasive sponge and a little detergent to make sure the stone will be like new again.