Each bubble structure in the open-celled foam generally consists of 14 reticulated windows or facets. The polygonal opening through each open window is referred to as a “pore”. In any given bubble, the polygonal pores actually are of two or three different characteristic sizes and shapes, but for material designation purposes, they are simplified to an average size and circular shape. The number of these pores that would subtend one inch then designates the foam “pore size”. Duocel® metal foams are generally manufactured from 5 to 40 pores per inch, while Duocel® carbon and ceramic foams are manufactured from 5 to 100 pores per inch. An average pore diameter is about 50% to 70% the diameter of its parent bubble, thus a 10 pore per inch (PPI) foam would have roughly 5 to 7 bubbles per inch.