The benefits of rotationallly molding a tornado shelter can be seen in this video about features attributed to the manufacturing process. Long lifespan, low maintenance and easy installation are just a few benefits of choosing a roto-molded shelter over other materials. Less capable materials, such as steel and fiberglass offer limited protection, as they both succomb to the long term effects of mother nature, namely water and moisture. Polyethylene being an inert material means it will not react with other materials. The best value for your family's near absolute tornado protection is the Granger ISS!