HM Digital TDS Handheld Meter with Carrying Case is ideal for residential and commerical use. It includes a carrying case with belt clip and a a TDS (Total Dissolved Solids) chart sticker on the back of the meter that explains TDS values and a built in thermometer. The meter shuts off automatically after 10 minutes of non use to conserve batteries and features a large LCD screen so it is easy to read your results. Factory calibrated. Can be recalibrated with a mini-screwdriver.