A seat structure may be installed in a seat assembly. The seat structure may comprise plurality of tube members forming a substantially closed structure. Some of the tube members have a substantially uniform cross-sectional area along a substantial portion of its respective longitudinal length. At least a first set of the tube members has at least one of a different dimensional property and a different material property from a second set of the tube members such that mechanical properties of each tube member is configured for stress requirements for a respective region that the respective tube member occupies. The plurality of tube members are joined such that the plurality of tube members are in fixed positions relative to each other.