The HydroSensor II is an easy, collapsible moisture detection tool. Map the migration of water in carpet and pad. It extends to 31 in. (79 cm) to save your knees and back - and collapses to 21 in. (53 cm) for convenient storage. A sensitive sensor system with nickel-plated tips sounds an alarm if the moisture content is above 17%. For use only on carpet and pad.