4 X 500MM x 610mm x 25mm CALCIUM SILICATE INSULATION BOARDS. 500MM x 610MM. PERFECT FOR INDOOR FIREPLACES SURROUNDS CANAL BOAT S INSULATION UNDER THE BASE OF AN OUTDOOR WOOD FIRED PIZZA OVEN. The exceptional heat resistance makes this able to withstand continuous heat cycles to the full service temperature limit and the low thermal conductivity provides maximum insulation throughout the temperature range - making it the ideal product when building custom fireplace enclosures or for insulation under the base of outdoor pizza ovens.