Southwire Romex Brand SIMpull NM-B (non-metallic sheathed) cable may be used for both exposed and concealed work in normally dry locations at temperature not to exceed 90 deg C (with ampacity limited to that for 60 deg C conductor) as specified in the national electrical code. NM-B cable is primarily used in residential wiring as branch circuit for outlet, switch and other load. NM-B cable may be run in air void of masonry block or tile walls where such walls are not wet or damp location. Voltage rating for NM-B cable is 600 V.