When I first started honing and restoring edges, I didn’t want to invest too much in stones (that has changed owing to a short but intense bout of HAD) and bought a set of 3 DMT credit card sized diamond hones when they were on sale on Amazon. They worked quite well as slurry stones until I was able to get hold of a decent BBW/coticule combo slurry stone to go with the combo coti I had inherited.

The cards are an inconvenient size for full size stones, but work great to clean or raise a slurry on my 6 x 1.5 inch coti.

I still carry those cards in my go bag for camping. They touch up the edge of a knife or a hatchet very nicely.