Cylinders for your AEG replica of brands like Action Army, Prometheus, Guarder and Eagle Force.
The Cylinder in an Airsoft device which ensures that air pressure can be built up inside the gearbox so the bb can be fired.
There are different types of cylinders such as for specific replica's like the M4, MP5, AK etc which still use the standard length barrel, but also cylinders which are linked to the length of a barrel. So if you have a barrel that is longer than the standard lenght it may be that if you want to upgrade your cylinder, you need one that is compatible with your length barrel.
