RUTLAND Dry Mix 211® is a refractory mortar ideal for joining or repairing masonry flue tile in any gas or wood fireplace and wood, coal, or pellet stove chimney. Just add water, mix, and trowel on to seal and join flue tiles. It can also be used as a parge coating (thin overcoat) when building fireboxes to give your fireplace a nice, even, dark gray finish. Does not require (but is stronger with) heat curing.