PTFE ,The use of PTFE (polytetrafluoroethylene) Coated Nut Black Color nonstick coatings is a two part system. Two coats are applied to the bolts, first a primer and next as a topcoat. Both PTFE coatings are essential to the long-lasting life of the fasteners. PTFE Coated Nut Black Color possess the highest operating temperature of any fluoropolymer. Added benefits are a low coefficient of friction and good chemical resistance.