This TDS (Total Dissolved Solids) meter is designed into the size of a marker pen for measuring the combined content of all inorganic and organic substances contained in molecular form in a liquid and reflects the degree of purity of fresh water. Its minimalist style and glossy seamless case is water-proof, easy to clean and user-friendly. As it only requires sticking the pen into a cup of water and pressing the TDS button to get the result figure, the operation is simple and intuitional. It enables fast check of any tap water to ensure pure water quality for daily usage in water-contaminated residential areas.