Usage: Test the purity of filter water quality, check your water filter performance, check its hardness, make sure you always drink pure water.(Please receive the promo code on the product page when of purchase to get a better price.)Fast and Accurate Readings: turn it on, dip in liquid and read the display, no need to work with color charts or test strips; a large LCD display makes it easy to read. 3 in 1 function: temperature switching (automatic temperature compensation); Shift between TDS and conductivity with the "shift" switch Portable Design: Pocket pen style and compact carrying case make it easy to put in your pocket or bag and go anywhere. Wide Application: Ideal for water purifiers and filters, food and beverage (food, vegetable) quality monitoring, swimming pools and spas, aquarium, hydroponics. Note: Data is All manual measurement, please allow 1 - 62cm error, due to the light and display difference, there will be some color difference, depending on the physical object received.