SinoWare PH Tester Digital PH Tester Water Red Large LCD screen, glass probe, 0.01pH readout accuracy, 0.01 Resolution, easy to read in the dark Great for home and laboratory pH testing applications including aquariums, swimming pools, and tap water Features ATC (Automatic Temperature Compensation), Replaceable Electrode and Long battery life No calibration needed for new purchased unit. Easy to calibrate with the pH 4 & 6.86 buffer packets Handheld pen-type design for portability and convenience with carrying case