This is a marvelous sharpening system. It is inexpensive and although won't put as nice of an edge as the Norton Waterstone system Norton Waterstone Starter Kit: 1) 220/1000 grit stone and 1) 4000/8000 grit stone, 1) SiC flattening stone it is a lot cheaper. I like these and use them for a convenient portable sharpener. I have sat in coffee shops and such and sharpened with these because they fit so well in a pocket. They don't require any lubricant but it is best to rinse them off after use (I used the drinking fountain at college) although you can do several uses and just wipe them off with your finger, water rinsing only once in a while. The coarse will put an edge on a very dull knife, if it is not too bad use a proper honing motion, but if it is really bad I "scrub" the blade with the card to make it work faster first, and then do the traditional motion when it is closer to an edge.

If you use the coarse until the edge will catch on your fingernail at the shallowest angle permitted by the blade, then use the fine until the blade will cut hair off your arm, and finally use the extra-fine until the edge shaves nicely, you will get a satisfactory edge, but make sure you check along the entire edge, not just one point. If you progress too quickly through the grits, it is much harder to get the blade razor sharp. I use adequate pressure with the coarse, lighten up a little for the fine, and just glide along the extra-fine. Razor-sharp is possible with these cards but it does take a little to break them in. At first they feel rough and will feel smoother after use, but after use they work better, faster, and can make things sharper.

Note these also work well in the kitchen.

Another note is that the DMT diamonds are mono-crystalline, which is better than the cheaper poly-crystalline diamonds that do not last as long or work as well.

I like these and they work very well for what they are, but prefer my waterstones for getting an edge that makes hair fly off my arm in fear.

I bought this little kit in order to have a super lightweight and small size diamond sharpener I could keep in my pack or wallet and never know it was there. For that purpose they are great. The coarsest one is still really not coarse enough to put an edge on a super dull knife, but you shouldn't be venturing out with a dull knife anyway, and it's got more than enough to grit to keep a sharp knife honed up during use.