Got it, Tried it. Sucks so far!!
Seems easy enough to do. Right range. Easy to read color chart. Little expensive but might be a nice way to see if you water is missing K or way overdosed.
Hard to get this kit and it costs around 30$. I had to buy mine from the only US distributor directly. PM me if you need more info.
I tested it on Aquarium water that I have been dosing K in, On RODI water, and the Same RODI water that had been soaking with CC for a week. They all show the same 18 ppm, Even the DI water. The test did not seem to increase when I added a drop of potassium solution directly to the vial. I may play with it later but for right now it's 2 thumbs down. Expensive, Hard to get, Doesn't work.