This is a great sharpener for badly damaged edges. It it NOT intended for good edges that need touching up. I've owned and used both a coarse and fine Diafold for serrated edges for at least ten years, and I think the two make a winning combination.
If you need to keep a sharp knife sharp, get the fine grit DMT sharpener. But for the times when your knife, hatchet, etc. needs serious help, this is the tool to grab. It is tapered for use on serrated edges but works fine when used like a sharpening steel on just about anything.
Pair this tool with a fine Diafold sharpener and you're all set. If you need something surgically sharp, add the extra fine sharpener as well. Only use the coarse sharpener when you need to set an edge, or as the initial sharpener for an axe or hatchet.
Just today I used this tool to set the edge on my well-used hatchet (Gerber Sport Axe) then finished with a fine Diafold sharpener. After just a few minutes, my hatchet was not quite shaving sharp but was able to take a few hairs off my arm... not to mention effortlessly split kindling and handle small "chopping chores". After sharpening the hatchet, I used this tool to set the edge on the serrations on my high dollar, fancy pants Benchmade 730S folding knife. This is something I do no more than once a year. Trust me, I would not use the coarse Diafold sharpener on my "pride and joy" unless I had complete confidence in it.
Get this, get the fine and maybe extra fine sharpeners, and you, sir or ma'am, are all set.