Plant Nanny Easy-Fill watering stakes are made of porous terra cotta and release water slowly beneath the soil surface near the plant’s root system. Subsoil watering promotes deeper and hardier root development. Easy-Fill stakes use an open topped plastic bottle (not included) as a reservoir. These can be filled quickly with a watering can or a hose. The Easy-Fill Quick-Connector adapter is designed to fit a wide range of bottle sizes. The adapter's rubber seal is designed so that the bottle will make a tight fit when pressed onto the rubber seal. Sold as a set of 3. Good for indoors/outside use.