This is a small version of the sharpening steel you might have in your kitchen for maintaining the edge on your kitchen knives.
At just 7.5cm long this high quality stainless steel sharpening steel if the perfect companion to a pen knife and can easily be carried in a backpack etc.
Sharpening steels do remove material from the blade edge so can be used to sharpen a dull blade. I prefer using them to maintain the edge. So a couple of strokes on the steel if I've been using the knife for a long period of time or can feel any burrs on the edge. For more serious sharpening I'll switch to a wetstone.