The pen ORP meter is professional and ideal tool for testing your water level. Suitable for aquarium pool and environment water.Features:Use to measure the amount of Oxidation Reduction Potential (ORP) level.The tendency of the solution to either gain or lose electrons.Clear LCD with backlight.Apply in water sources， aquarium， hydroponics， spas， swimming pools and other water systems.Compact and portable pen-type design.Easy to use and provides instant display of results.Specifications:Range: -1999mV ～ 1999mVResolution: 1mVAccuracy: ±5mV Operating Temperature: 0℃ ～ 50℃ (32°F ～ 122°F)Battery: 4 × 1.5 V (AG-13) Button Cell Battery (not included)Color: GreenMaterial: ABSItem Size: 15.1 * 3.3 * 2cm / 5.9 * 1.3 * 0.8inItem Weight: 52.4g / 1.8ozPackage Size: 17.8 * 7 * 3cm / 7 * 2.8 * 1.2inPackage Weight: 108g / 3.8ozPackage List:1 * ORP Meter (Battery is not included)1 * User Manual1 * Mini Screwdriver