Ground Wire: Paper Wrapped vs Molded PVC Differences

NM-B cable can look different on the inside, and that often sparks unnecessary debate. Some NM-B uses a paper (kraft) sheath to bundle the conductors, while other versions use a molded plastic filler. This difference comes down to manufacturing methods and design preferences—not performance or safety. Paper-wrapped NM-B has been around longer and is valued for its flexibility and ease of pulling through studs and conduit spaces. Plastic-filled NM-B is a newer approach that offers a cleaner, more uniform interior and slightly better resistance to incidental moisture during installation. Visually and tactilely different? Yes. Electrically different? No.

From a compliance and safety standpoint, neither option is better—they’re simply optimized differently. Both paper-sheathed and molded-plastic NM-B are 100% compliant with the NEC, fully UL listed, and meet RoHS requirements. Ampacity, voltage rating, and approved use cases are identical. Inspectors don’t prefer one over the other, and neither provides a performance advantage once installed. The real choice comes down to installer preference: paper for flexibility and easier pulls, plastic for durability and cleaner handling. Same code, same safety, same job—just different ways of getting there.