I agree completely with f-e . I use the Apera PH60 and have been happy with it. It gets used every single day. Keep it clean and recalibrate weekly. I replaced an older Apera with the one I have now after a Replacement Probe wouldn't work. Probe costs about 2/3 of the entire unit, so I just returned the Replacement Probe and ordered a new meter. Found a sweet deal on a more expensive Hanna meter, but it sits unopened since the Apera continues to work fine. It drifts about .15 between calibrations.