This Thirsty Light HGTL is a digital soil moisture monitor that blinks an LED to alert you when it is time to water a potted plant. Designed to be unobtrusive when left in the soil of a plant, it continuously tests the moisture level once per second. As the soil gets dryer, the light blinks faster. When it reaches the fifth level, completely dry, the Thirsty Light goes into standby mode to conserve electricity, emitting a double blink every three seconds. The soil probe is made of corrosion resistant brass, and it has a tough ABS plastic casing. It has an ON/OFF switch to conserve battery life when not in use. The digital moisture meter includes two replaceable AG13 lithium 1.5-volt batteries and a watering guide. Backed by a 30 day manufacturer's warranty.