No batteries or electricity needed, plug and use. This water level gauge is used for flower pots. It can display the water level to remind you of watering. When there is no water in the pot, the buoy of the water level gauge will be at the bottom. On this note, pull up the water level and water plants through the hole. Simply insert the level into the soil, and it will help your plants grow healthy and strong. An ideal tool for indoor and outdoor use. Specification: Material: Plastic #1 Size: Approx.17.5cm/6.89inch #2 Size :Approx.34cm/13.38inch #3 Size: Approx.20cm/7.87inch #4 Size: Approx.22.5cm/8.85inch Package Includes: 2 Pieces of Water Level 17.5cm 2 Pieces of Water Level 34cm 2 Pieces of Water Level 20cm 2 Pieces of Water Level 22.5cm Note: Don't pour too much water, it is better to let the buyo below the top water mark.