Greentherm 23 LI Medium Duty Brick (2300&ordm;F) Insulating Fire Brick for Gold Melting Furnaces Kilns Foundries and Casting Gold Silver Copper 2300F Insulating Firebrick Used for Furnace Applications Size: 9" x 4-1/2" x 2-1/2" Great for Homemade Melting and Forming Forges