I had a retractable diamond file that wasnt seeing much use so i decided to replace the file with a ferro rod. Very easy to do. I had to grind down an 8mm blank to 6mm to fit but it only took 10 mins on the bench grinder. Works really well and you can still put it back to a diamond file at a later date if needed. I particularly like the pen clip so you can put it in the pen pocket of your shirt out of the way.