Etekcity Digital pH Meter, 2 Pack 2011 Plus High Accuracy Water Pen Tester Pocket Size Design with ATC (Automatic Temperature Compensation), 0-14 pH Measurement Range (Red) Great for all home and laboratory pH testing applications including aquariums, swimming pools etc 0.05 pH highly accuracy; reliable and quick readings with clear Backlight LCD screen Features ATC , Replaceable Electrode and Long battery life for years of use No calibration needed for new purchased unit. Easy to calibrate with the pH buffer packets Handheld pen-type design for portability and convenience with carrying case; CE/FCC/ROHS Approved