A seat assembly including a seat base, a back support, a support for the back support and/or for the seat base and at least one elastomer torsion-spring element. The back support and/or the seat base are/is pivotably hinged to the support in such a manner that a pivoting movement of the back support and/or of the seat base on a rotation axis can be carried out. During the respective pivoting movement of the back support and/or of the seat base with the elastomer torsion-spring element a restoring torque is generated that acts on the back support and/or on the seat base. The elastomer torsion-spring element includes an internal casing, an external casing encompassing the internal casing, and an elastomer body arranged in a space between the internal casing and the external casing. The elastomer body is rigidly connected to contact surfaces of the internal and external casings. The internal casing and/or the external casing are/is rotatably arranged on a rotation axis. During rotation of the internal casing and/or of the external casing on the rotation axis deformation of the elastomer body occurs. The contact surface of the internal or external casings include a non-circular cross section in a sectional plane perpendicular to the rotation axis.