AN IMPORTANT NOTE: This tool and its accessories are designed for use with Woodland Scenics own high-density, nontoxic expanded polystyrene foam. Since many foam products emit a toxic gas when heated, this tool should never be used with ordinary Styrofoam, foam rubber or other foam products. Transfer your track plans and layout diagrams to wood, foam or other surfaces with these special pencils. Soft leads will not damage foam products and are made from special compounds to prevent colors from bleeding back through porous coverings. Each pack includes two red and two black pencils so you can color-code your markings.