This little tool works far better than it looks as though it would. The diamond tip is powered by a couple of AAA batteries (included). It is very easy to use and will engrave most surfaces including metal, glass, ceramic plastics and many more. You just use it like a pen with very little pressure like a fountain pen.
We, obviously, use it on bikes and whilst we haven't had any desire to engrave glass or ceramics, we have used it on plenty of motorcycle parts. If you're striping a multi cyclinder engine you can use it to mark up the pistons. Price at less than a modest round in a pub, it will pay for itself in short shift. We refused to give back our sample from Laser Tools as it was far too useful.