Product Description:Use Orton Pyrometric Self-Supporting Witness Cones to make sure your kiln is firing to Cone 04. Cones feature a built-in base with correct height (1 3/4") and angle (8 degrees) to help ensure reproducible firings. We recommend putting cones in each firing to ensure your kiln is firing correctly every time. Place 1 cone on your top, middle, and bottom shelf to ensure all areas of your kiln are reaching Cone 04. A perfect arc that just touches the kiln shelf indicates the kiln fired to Cone 04. An arc that slumps onto the shelf means the kiln fired above Cone 04. An arc that doesn't touch the shelf indicates that the kiln fired cooler that Cone 04. Each box includes 25 cones.