This coupler can be used to join two pieces of CO2 tubing. Compatible with CO2 tubing sold by Nature Aquascapes.
Intense Mini CO2 Regulator
Advanced Precision CO2 Bubble Counter-Inline With Magnifying Holder
Precision Atomic Check Valve Stainless Steel - 100% Stop
Intense Atomic Inline CO2 Diffuser
Intense Precision Atomic+ CO2 Diffuser (With Built-in Check Valve)