I have several PH meters for different aquariums. I got Milwakee 2 years ago and still works great and accurate with only about 1 or 2 calibrations in 2 years.When I got another milwakee meter it was innacurate even with calibration, sent it back got a replacement and I was not able to calibrate it ever. Sent it back.Still ordered one more to see if I had just received 2 bad units or bad probes and the las one I got is working fine and accurate.In the process I got a different brand PH monitor half the price that uses batteries instead of DC and not only measures accurate PH but also very accurate temperature and it has a back light so my message to Milwakee is make sure your quality doesn't go down and add back light to you meters and temperature reading because you have a new ( I guess is new ) competitor with a better product for half the price! I don't know how long this new meters will last from either Milwakee or the other brand but trust me if any of the 2 break I will update this review.This is my second unit. Its so accurate for aquarium use. Calibration is a cinch!! Well made.... now i have one complaint. The lcd screen needs to be backlit... its dark and hard to read...Used to monitor PH in aquarium and does a great job, very accurateAmazing productWorks great! Using to monitor small reef tankWorks greatexcellent product from Milwaukee, very accurateGreat product