1413μS/cm Calibration Solution Conductivity Standard Buffer Solution for EC Tester Hydroponics Meter 4 Bottles of 50mL

Used these to help calibrate a linear-only HI 9033 meter. Post-calibration, it agreed with (<1% error) the other calibration solutions from this manufacturer across the full range (1413µS,5000µS), so these are indeed pretty accurate. These should do fine if all you need is a generic non-certified calibration done.

This is a nice pack. Since you have to use so much of the calibration solution, it's nice to find a 4 pack. It's all premixed, just open the bottle and go. Seems fairly accurate as well.

I’m using this to check caliber on some meters we use with our hydroponic garden and aquarium. The tiny bottles are great because this stuff should not be held long term after opening. We use about 25 ml for each calibration, so we get two uses per bottle.They are very tightly sealed and the results look good. With a new, factory calibrated meter I got 14.1 mS/cm, which is as good as that meter gets.My only concern is the lack of lot numbers or production/expiration dates. This isn’t lab grade stuff, but it would be nice to have a sense of how old this is.

I have a hydroponic garden so it is critical to keep my EC tested calibrated to ensure a strong harvest. The UIUZMAR 1413μS/cm Calibration Solution was a great kit to ensure I can continue to get the most from my garden set up.The solution came in four 50ml bottles which had wide mouths and allowed for my meter to easily slot in. I appreciate that the solution came in four separate containers, so that I can use one and keep the others fresh for future use.The solution allowed me to quickly recalibrate the meter, so I was good to go! (I realized I didn't capture the final calibration moment in the image, so ignore the reading, I can attest the solution calibrates correctly)My only (incredibly minor) negative feedback is that the protective seal didn't have any form of easy open option, so I had to puncture the top with scissors to get the solution open, but at least it was sealed tightly.

These reference calibration solutions are the ones recommended for my hydroponics nutrient meter of the same brand. Each bottle is "single use", presumably because conductivity of the solution may change through evaporation or contamination. Calibration doesn't need to be done regularly, so I expect four bottles will last me four seasons.

So I can attest to its accuracy as I have just tested it with a brand new factory calibrated meter. It measured spot on. My complaint is I’m new to using such calibration solutions and the manufacturer offers little help on storage conditions after opening or sealed bottles. I’ve read that shelf life is 2 years unopened but I have no idea of the manufacturer date or expiration date. What’s the shelf life after opened? Is it a one time use? These are things that I would expect to be addressed or documented but these come with no paperwork of any kind. Seems pretty expensive if it’s a 1 time use solution and wasteful as you do not need but about half a bottle to submerge your probe.

Personally, I've never had a problem with unopened 1413μS/cm calibration solution going "bad" after 2 - 3 years, BUT they are supposed to be used within a year of manufacture. As other reviewers have noted there are no dates listed anywhere. I'm giving these 4 stars due to the price of sub $15 for 4 bottles. The bottles I received look brand new, so they were "probably" manufactured recently.