The HI 775 CheckerHC is a simple, accurate, and cost effective way to measure alkalinity in fresh water. Designed as a more accurate alternative to chemical test kits, the HI 775 provides quick, accurate results in four easy steps. 1.) Step One - Add a sample to the included cuvette(s) 2.) Step Two - Insert sample into the Checker and zero it out 3.) Step Three - Remove sample and add reagent 4.) Step Four ? Reinsert sample and click the button to measure your results or… - Press and hold the button for 3 seconds for a time reaction reading The HI 775 uses a colorimetric method. The reaction causes a distinctive range of colors from yellow to blue to develop. This meter has been developed to work with fresh water samples.. FEATURES/BENEFITS: * Small palm-sized design * Accurate from ±5ppm ± 5% of reading * Dedicated to a single parameter * Uses a single AAA battery * Auto Power Off after 10 minutes in inactivity * Built-in timer for timed reaction readings PRIMARY APPLICATIONS: * Water Quality * Education * Freshwater Aquarium * Environmental Order Information: The HI 775 CheckerHC is supplied with 2 cuvettes and caps, reagent starter kit (1 bottle of alkalinity reagent, 1 ml syringe), 1 x1.5V AAA battery, and an instruction manual