Cavity reinforcement materials are used in the automotive industry to stiffen hollow cavities in unibody constructions. Typical areas of use include the engine rails, rocker panels, roof support or any other cavity in need of reinforcement. Use of these materials can allow for reductions in vehicle weight without sacrificing long-term durability and stiffness. Additional NVH benefits could be gained through the change in stiffness and through acting as a physical barrier to the propagation of noise, water and dust. The objective of this paper is to describe the properties of a new type of cavity reinforcing material and to identify key properties of reinforcing materials.