Southwire Romex® Brand SIMpull® Type NM-B (nonmetallic-sheathed) cable may be used for both exposed and concealed work in dry locations as specified in the National Electrical Code®. NM-B cable is primarily used in residential wiring as branch circuits for outlets, switches, and other loads. NM-B cable may be run in air voids of masonry block or tile walls where such walls are not wet or damp locations. Voltage rating for NM-B cable is 600 volts.