This Advancer Nitride-bonded Silicon Carbide shelf is 26 inches wide (by 1/4 inch thick) weighs 9 lbs. These are incredible durable and strong. However there are cautions to their use. They can act as an electrical conductor so must not contact elements and should not be used in kilns with unpinned elements protruding from grooves. They must be stored in a dry place to prevent moisture penetration (which can cause a steam explosion during heatup). The company has a recommend drying schedule if shelves do absorb moisture (the application of kiln wash is not considered a prolonged exposure and is OK).
In the ceramic industry, cordierite is a man-made refractory crystalline material having extremely low thermal expansion.
In the ceramic industry, refractory materials are those that can withstand a high temperature without deforming or melting. Refractories are used to build and furnish kilns.