Bolted to the front of the 2008 Mercedes SLR McLaren Roadster chassis is a carbon fiber structure highlighted by conical side elements designed to progressively absorb accident energy. Each cone is approximately 24.5-in. long, and weighs 7.5 lb. The cross-section of the part varies from front to back to ensure that the structure collapses in a predictable manner and at a pre-determined rate, while using the minimum material possible in the production process. A similar structure is used in the rear on the approximately 3,900-lb. car, while its side sills are composed of multi-shell reinforced carbon fiber sections and the A-pillar wraps carbon fiber around high-strength steel.