Cost driven performance improvements for RIM fascia materials are desired by the automotive industry. This need can be met by combining the use of low cost fillers with high performance RIM polymers resulting in enhanced dimensional stability and surface quality while maintaining low temperature impact performance. A significant reduction in part thickness is thus possible, saving both weight and cost.This paper describes recent work where high performance polyurethane and polyurea polymers incorporating low cost fillers have been characterized at different part thicknesses. Properties examined include stiffness, thermal stability, dimensional stability, impact at low temperature, and painted surface quality. Data is provided for these systems at thicknesses of 4.2, 3.8 and 3.2 mm. An economic analysis is provided to illustrate the cost benefits of such material, filler, and down-gauging effects.