Rated to Cone 10. Manufactured of a high alumina mullite/cordierite mixture that yields a smooth, durable surface with good thermal shock resistance. When setters are pre-stacked, accepts plates up to 12.5" dia. & 1.5" high. Accepts plates up to 14" dia. when stacking setter, plate; setter, plate, etc. Buy 10 of any 1 kiln furniture item & pay 10% less.