Did you know a freshly packed silencer or muffler actually restores power? Owens-Corning fiberglass replacement packing keeps mufflers performing as they're meant to This Performance Packing is comprised of fine, blended interwoven fiberglass fibers made to FMFÆs specifications for high heat resistance, great sound attenuation and optimum performance and longevity. PACKING DUAL 4.1RCT CRF