Water indicator size S. Aqua Meter. This handy device tells us the level of moisture in the substrate of our bonsai. Thanks to him, we can easily know when it is necessary to water. Useful for all types of plants It is very easy to install, just place it nailed to the mark on the bonsai substrate. The color indicator will change depending on the humidity detected in the substrate. Features: - Easy to install - This is the first household humidity tester with pF indicator (water capacity available) - The small watering indicator is ideal for use in pots measuring at least 20cm wide or in bonsai trees up to 8 years approx. - Can be used on many types of substrates. - No batteries required and environmentally friendly. Directions for use: Blue: Enough water in the substrate. White: Need watering. Note: The watering indicator has a lifespan of 6-9 months.