(05/27/2009) - Is easy to calibrate. My first one lasted about 1.5 years and the 2nd one is already at 1.5 years and I am getting ready to calibrate it again. The 1st one only lasted that long because I dropped it and it broke, my bad. this 2nd one is working fine. I recal it about once every 6 months, and I also check my pH manually about once a month to make sure.

(09/17/2005) - I've had two different probes hooked up to my AquaControllerII in the last week; one from Premium and the other came direct from Neptune. Both of these probes "seem to be defective" (according to Neptune) as they've been calibrated several times (with Neptune's and Pinpoint's 7.0 and 10.0 packets) but still display values as low as 7.03 for my reef tank (which was in the middle of the day after dosing 2 liters of kalkwasser). Not only have I wasted several packets of reference solution, but now I have to pay to get both of them shipped back to San Jose so they can be tested or declared officially defective by Neptune. Last I checked, quality control is supposed to take place PRIOR to selling a product. And when known defective batches are sold, most companies offer to cover the customer's costs in order to fix their problems.

(07/11/2010) - Easy to use. Pretty much plug-n-play. My only complaint...the protective cap was a pain to remove for initial installation. Broke one of the tabs that surrounds the probe. Still works.