Lindemann Heat Stop, Pre-Mix - 15 lb. Refractory Mortars Developed for Installing Firebricks in Masonry Fireplace Installations Great For Any Project Involving Chimneys, Boilers, Furnaces, Kilns & More! Premixed Available in Fifteen (15) Pound or Fifty (50) Pound Containers! Dry Mix Available in Ten (10) Pound Container or Fifty (50) Pound Bag! These Mortars Meet & Exceed All Local / National Building Codes! Good for Applications Exceeding 2000 F