Southwire Romex brand SIMpull NM-B (nonmetallic-sheathed) cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90 deg C 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 V.