Features： Excellent meter very accurate and durable. With protective plastic case and calibration screwdriver. An ideal instrument for aquarium fishing industry swimming pool school laboratory food & beverage etc. In addition you must calibrate this tester whenever the following happens: ● If the tester was used or lay aside long time; recalibrate it ● It was used too often; recalibrate it ● Need High Accuracy. recalibrate it ● Note: You will Need calibrate after you get it. Specification: *Measuring pH Range: 0.0 - 14.0 pH *Resolution: 0.1 pH *Accuracy: ±0.1 pH (at 20°C/68°F) ±0.2 pH *Operating Temperature: 0 - 50°C (32 - 122°F) *Calibration: Manual 1 point *Relative Humidity: <95% *Life: Approx.700 hours of use *Size: 152mm x 30mm x 15mm (5.9x1.2x0.6 ) *Trimming: By potentiometer *Battery: 3*1.5v (AG-13 button battery) (included) *Net Weight: Approx. 57g (after installed batteries) Package: *1 x Digital PH Meter Tester Pen *1 x Calibration Adjustment Screwdriver *3 x Button Cell Batteries (included) *1 x User Instruction Manual (English)