A CO2 Non Return Valve prevents water from siphoning / back-flowing down aquarium tubing when pressure is turned off.  For example, when the air pump or CO2 system is switched off.  Without this device water will siphon down the tubing an enter your electrical equipment.

100% Brand new and high quality one way check valve for CO2 System.
Small and compact
Protect you CO2 System by preventing aquarium water from back siphoning during a outage and casing damage.
Easy to install
Compatible with standard aquarium air pipe of 4mm inner diameter
Material:durable plastic
Overall Size:53x15mm (LxW)
Color:Red , Clear