Coated in patented SIMpull Cable Jacket for easier pulling; stripping; and installation Romex Type NM-B Copper Building Wire is commonly applied in residential building wiring as a branch circuit for switches and outlets Installation above ground and in dry locations only. The voltage rating of the cable is 600 volts NM-B cable may be run in air voids of masonry block or tile walls where such walls are not wet or damp locations.