This is a block of Calsil. I cut a piece of it about the size of a kids shoebox, then cut it in half long ways, and hollowed out an area in each half, so that the Tx portion of the unit would rest in it, protected from the heat, and just let the wire and probe run out of the heat protected "box"
To test, last night, put the oven on 450*, and put the probe in the hollowed out block and left it for 30 min, it was not an accurate test, because the "L" shaped probe was larger than the hollow area, and i had about 1/8" gap between the two halves with the probe in between. After 30 min, the probe read only 130. I figure on a hot sunny day, beside the pit the Tx would be almost this hot anyway. Will try to test again tonight.