Teflon Expansion Joint, also known as metal bellows, bellows expansion joint, is the compensating element for thermal expansion and relative movement in pipelines, containers and machines. They consist of one or more metal bellows, connectors at both ends, and tie rods that depend on the application. They are differentiated according to the three basic types of movement: Axial, angular and lateral expansion joints.

Teflon Expansion Joint is elastic vessel that can be compressed when pressure is applied to the outside of the vessel, or extended under vacuum. When the pressure or vacuum is released, the bellows will return to its original shape (provided the material has not been stressed past its yield strength).