I just got one 2 days or3, Bluelab ph pen,it is a relief to know l am dealing with somthing that is good.like you do not have sec doubts about! Make sure you go to website to register it,then download the manual.Do not let the tip dry out,on the website it says if it dries it dies! As well make sure the fluids 7@4 you use them for.calibration.tells you in the manual.Good Luck be safe!