NEMA grades XP, XPC and XXXPC Paper Reinforced Phenolic -- natural color is typically light tan to brown. These grades are composed of a paper base impregnated with a phenolic resin binder. (Phenolics are the oldest, best-known general purpose thermoset resins. They are among the lowest in cost and easiest to process. Phenolics are quite adequate for a fair percentage of electrical applications.