A switch barrel is the barrel that can be exchanged with the existing barrel of a firearm.
Legally, a distinction is made between exchange barrels and switch barrels: An exchange barrel can be replaced by the hunter or shooter themselves, while a switch barrel requires a gunsmith to be installed.
A switch system includes not only the barrel but also the appropriate bolt, trigger unit, and possibly magazine.
A switch barrel is an essential part of a firearm and is treated legally the same as a firearm. Acquisition and possession are free for the holder of a firearms ownership card if they already own a weapon in the same or smaller caliber.