Designed for a learning environment that requires book storage coupled with mobility. CAL133 compliant shell with no added additives using the most advanced copolymer polypropylene material and 2" locking hooded, compression casters. leading edge CAD technology has produced the most attractive, flexible, and comfortable seating in the industry. The smooth back and rib-less design adds to the comfort and flexibility of the chair. With hundreds of thousands serving students all across America, Silhoflex chairs now offer book storage and mobility.