Compatible with for DUO/Terra/ Art quick connect machines, it can connect the soda water machine and Blue Co2 Cylinder.All types of CO2 cylinders can be used. With this quick adapter, you can continue to use traditional screw valve CO2 cylinders.You can also use this adapter to connect old soda hose with TR21-4 Male Thread to new soda water maker.This adapter can be used with almost all 425 gram aluminium CO2 cylinders with screw valve from different suppliers.With just one hand, your CO2 aerator (type DUO) can be used with this adapter.The co2 adapter is made of copper, anti-corrosion, durable and safe, with polished surface, good sealing, high quality, anti-oxidation, anti-rust.Thread: TR21-4Height: 37mmOuter diameter: 36.5mmColour:copperMaterial:copperPackage Contents:1 x Quick CO2 Adapter1 x GasketOnly the above package content, other products are not included.Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.