This is for 2 sq. ft. (1x2) It is 1" thick.
This material can be used to shield flues or bell caps from heat which may be too intense. It may be needed any place you are trying to cut the heat intensity. This is what is placed at the top of the heat riser in the castle builds to protect the flues. It is also used in the Derrick build to prevent too much heat from radiating out through the barrel over the heat riser. It can be used inside barrel of rocket mass heaters to slow heat radiation and pass more of the heat to bench. It is also used around the oven to keep the heat in the oven and not radiating out.
This is arguably the best insulation (highest R-rating) for its thickness available. This material is also available in a 1/2" thick blanket.