Which of your products is the best choice as joint material for the installation ?

Which of your products is the best choice as joint material for the installation ?

Heat Stop II and Heat Stop 50 are the best refractory mortar products for installing clay flue lining and firebrick because they are completely non-water soluble in service after the initial set. They have an indefinite shelf life, and excellent drying characteristics no matter the humidity. These products are specified by NFPA-211 (National Fire Protection Association), in addition to meeting all local, regional and national building codes.