"Caliber" refers to the specific size of the tile. As the tile passes through the kiln during the manufacturing process, it will have all the moisture burned off in the intense heat. When this happens, the tile will shrink between 5% and 10%! The amount of shrinkage during manufacturing depends on the specific tile composition and temperature in the kiln. The factory then separates the tiles into different "Calibers" to ensure the installer has similar sizes provide the best-finished product. It’s important to note that when beginning your project to ensure your tile has the same caliber to avoid potential issues. Please reach out to a store associate or Customer Care Center if you have additional questions.