The size of the Oxygen Concentrator needed depends on the size of the Cage you are using.
Small and Medium Cages can utilize a 5 Liter Oxygen Concentrator or a 10 Liter Oxygen Concentrator. Large Cages must utilize a 10 Liter Oxygen Concentrator. Please note, Pawprint Oxygen Canisters cannot be used with the Oxygen Cage.
Here is a detailed explanation on why this is the case:
The Oxygen Cage requires the Concentrator to adequately provide the correct amount of air flow into the Cage. When using the Concentrator with the Cage, you will always set the Concentrator to its highest flow rate. This means that you will set the 5 Liter Oxygen Concentrator to 5 Liters per minute when using a Small or Medium Cage or set the 10 Liter Concentrator to 10 Liters per minute when using a Large Cage.
Think about it: As you go from a Small or Medium Cage to a Large Cage, you have to fill up a greater volume of space while also ensuring that you are turning over the air in the Cage, pushing out the excess CO2 and other gaseous by products, while continuing to push fresh oxygen gas into the Cage. For these reasons it is essential that you use higher flow rates when you the Cage then you would if you were administering oxygen therapy in a different way, such as flow by mask.