This E2613/E2614 seat back is constructed of solid birch, nylon or fi berglass shell with soft, medium or hard Sunmate foam. Includes a stretchable, breathable, moisture-resistant Darlexx cover. Can accommodate optional laterals, head positioning systems and harnesses. Hardware is made of aircraft steel and/ or nylon glass-reinforced plastic in fi xed or quick-release models. This planar back is for users who want fi rm, but comfortable, support.