Cor-Pak® 1-MUL bags contain VpCI® (Vapor Phase Corrosion Inhibitor) to protect ferrous and non-ferrous metals from corrosion. Cor-Pak® 1-MUL bags are approved for military use per NSN # 6850-01-470-2737. The Tyvek® membrane allows the VpCI® molecules to reach the metal surface. * Tyvek is registered as a proprietary trademark of Dupont.