Sustee Aquameter (White, Medium) - Plant Soil Moisture Sensor - Best for Potted Plants &ndash; Probe, Meter, Indicator Senses water at root level, no dirty fingers & damaged roots trying to gauge moist soil by feel Leave the device in the pot to continuously monitor soil humidity and show you when to water Prevent withering & root rot, so your healthy houseplants can clean indoor air to keep you healthy! Award-winning product design - No batteries  Environmentally friendly  Creates little waste Sustee size M is best for pots 4.7 to 7 inches in diameter. See Product Description for more info