FireGuard ceramic flue liner is certified, listed and labeled by Guardian Fire Testing Laboratory, Inc. (ISO 17025) as a repair system for damaged or defective clay flue liners. The FireGuard system is the only certified, ceramic resurfacing and joint repair system employing pinpoint vibration which promotes maximum penetration of tight joints and fractures while ensuring a consistently smooth, even finish. FireGuard's temperature rating, 3,205° F. It's unique chemical and physical properties form a surface that effectively resists extreme heat, acids and water. When properly installed, FireGuard will solidly fill all gaps and fractures in the clay liners, virtually eliminating the possibility of heat transfer or the seepage of dangerous gasses. (Must combine with FireGuard Blending Agent)