All inter braided construction, Style 357 utilizes a resilient, “springy” carbon center around which the exfoliated carbon-inserted foil is braided while laying very high strength, silky carbon yarn in the corners. This choice of materials and construction enables the surface of Style 357 to overcome the plating effect, common with exfoliant foils alone. Not only is the matrix spring-like, the outer-edge carbon yarns prevent migration of the foil to the stem or sleeve and improves the actual sealing effect. In addition, this particular layup and materials choice yields a much denser product than exfoliant foils alone can yield. This culminates in a product that retains a very high percentage of both its weight and volume even at the highest temperatures and pressures. Style 357 passes API Standards 622 certified, Process Valve Packing for Fugitive Emissions, test requirements.