Fire clay which is a refractory type mortar designed to be used with fire brick for applications subjected to high temperatures such as chimney’s, fireplaces and bread/pizza ovens. This is the ideal mortar for the firebrick and clay flue installations and also for repairs and restoration.  Heat Stop 50 one of the most popular and economical Heat Stop products, this dry-mix refractory mortar is made from high temperature cements and selected aggregates to be a superior product for you project.