Southwire Romex® Brand SIMpull® Type NM-B Cable 12-3Nonmetallic Sheathed Cable. 600 Volt. Copper Conductors. Color Coded Jacket. SIMpull Jacket Designed for Easier Pulling. Application 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 90C (with ampacity limited to that for 60C conductors) as specified in the National Electrical Code. NM B cable is primarily used in residential wiring as