For plastics containing fillers, WS₂ requires a Durillium substrate that better enables it to resist the wear of the solid particles. The Durillium substrate can prolong the service life of the plastic wetted surface by an order of magnitude (x10)   over the WS₂ treated surfaces. In situations where chrome, electroless nickel, TiN, or nickelon are used as a mold coating, WS₂is not to be used in conjunction with plastics with hardnesses below 100 Durometers or with rubber. For these, Russell's Permalon Fluoropolymer coatings have been proven to be state of the art.