This is amazing! The refractory slate at the back of my fireplace was cracking and crumbling, and after speaking to almost every Home Depot employee, I got the impression that there was no such thing as "fire mortar" or any cement-like material to patch the fireplace. I called the guy for an estimate and he wanted to charge me $250 to replace the panel. After three different meetings with this guy, and he never showed up at any of them, I decided to try again to find material similar to the patch. I stumbled across this at Revain and for a fraction of the cost of repairing it from a man who never shows it was worth a try. It worked great! I was able to patch every crevice and even the corners of the firebox (where the plates didn't quite touch) and I only used half a bucket! 2 winter seasons and still holding up.