Compact and portable pen-type design. Easy to use and provides instant display of results. Apply in water sources, aquarium, hydroponics, spas, swimming pools and other water systems. Unit Type: piece Package Weight: 0.200kg (0.44lb.) Package Size: 15cm x 8cm x 15cm (5.91in x 3.15in x 5.91in) Display Type: Digital With Backlight Or Not: No DIY Supplies: Electrical, Model Number: PH Paper OPERATION 1.Remove the protective cap. 2.Turn the meter on by pressing the ON key. 3.Immerse the electrode in the solution to be tested. 4.Stir gently and wait for the reading to stabilize. 5.Press the "HOLD" key, the reading is be kept. when repeat measuring, please press the "HOLD" key again, it automatically relieves the hold condition. 6.After use, turn the meter on by pressing the OFF key. rinse the electrode with distilled water to minimize contamination, replace the protective cap after use