Airsoft Outlet Northwest writes about understanding cylinder size and barrel lengths for those who want to do upgrades... "With the plethora of airsoft upgrade parts available, a lot of new (or experienced) AEG owners feel the drive to customize and upgrade their guns. Sometimes this even means modding new, unfired AEGs to work 'better'. One of the most common modifications is a new inner barrel. Especially in some brands, this is actually a very good idea.