"It was installed when we built our house, circa 2006. It is made of French stone and has has a honeycomb shape (the inside portion that is). It is alleged by them (the manufacturers) that this particular stone retains heat better than most, so the baker does not need to feed the fire as often. It came as a kit, but the builder put it all together. The outside stone is from a portico on one of the buildings on our property which fell down. The stone mason built this around the honeycomb inside kit. It probably took a few days to build because the granite had to be cut and fitted around the oven."