Thanks for offering this contest!
I am a big advocate of the Hannah Checkers. I enjoy testing (as much as one can) with the checkers rather than the test kits that you need to count the drops and then match up the colors to get your reading. The checkers are right on with the test results. I already have the calc and alk checkers but would especially like the digital refractometer. Wouldn't mind the other ones I don't have already either.
I own the alk and PO4 checkers. Love them both and you can not beat the speed of the alk or the low range of the PO4. No guessing what shade of color you have cause these bad boys just give you what you want.....the numbers! Would love to add the Ca checker to my current test kits.