4″ breaker plates were filled with Polyurethane, which was completely removed after 30 minutes at 850F. 4″ Breaker Plates Filled With POLYURETHANE2015-02-102018-04-23https://accuthermal.com/wp-content/uploads/2024/01/accuthermal-header-logo.jpgAccurate Thermal Systemshttps://accuthermal.com/wp-content/uploads/2015/02/blog3-dirty.jpg200px200px