Digital pH Meter Tester - Universal Tester! 1. Pen-type PH Meter 2. Lightweight and compact 3. Quick accurate readings 4. Membrane switching 5. Long Battery Life This handy pH pen/meter is a great tool for any aquarist. It is extremely easy to use and is waterproof. Simply dip the meter in the solution to get the pH reading. Its high accuracy and resolution also make it suitable even for the most-demanding applications. Note: pH 7.0 solution is required for calibration. Specifications: Large Readout Display Range: 0.0-14.0 pH Resolution: 0.01 pH resolution Accuracy: +/- 0.02 pH Fixed Electrode Operating Temperatures: 5`C to 50`C ATC: Automatic Temperature Compensation for accurate readings! Power Supply: 3 x 1.5 Volt (Button Battery) Battery Life: 500 hours of continuous use Size: 6" x 1.00" Largest Diameter Weight: 70 Grams Waterproof Mini PH Tester (0.01 pH resolution) - Totally waterproof! - Small like a pen! I am the manufacturer of the YM Instrument Co.,Ltd.