Nature: When the same liquid in the communicating vessel does not flow, the liquid level in each container directly in contact with the atmosphere always maintains the same height. Connecting device: the upper opening is not connected, and the lower connecting container Principle: The principle of the communicating device can be explained by the liquid pressure. Therefore, when the liquid is not flowing, the liquid level in each container of the communicating device should be kept flat. Size: 10.3*15*18.5cm/4*5.9*7.2in