What are the standard dimensions of firebrick?

Firebrick, commonly used in high-temperature applications such as furnaces and fireplaces, traditionally has standard dimensions that cater to its specific usage requirements. The answer indicating dimensions of 2 1/2 x 4 1/2 x 9 inches is consistent with industry standards, which prioritize both strength and thermal insulation properties. This size allows firebrick to effectively withstand extreme heat while also being manageable for construction and repair tasks.

In various building codes and manufacturing standards, the dimensions are not only dictated for efficiency in stacking and installation but also for ensuring the performance of the brick under thermal stress. The other dimensions provided do not align with the commonly accepted size for firebrick used in professional applications, making the dimensions stated in the selected answer the most appropriate and widely recognized among industry practitioners.