 Regularly spaced, the protruding air-filled hemispheres are known as "bubbles" which are 1/4 inch (6 millimeters) in diameter, to as large as an inch (26 millimeters) or more.Air-bubble packing was co-invented by Alfred Fielding and Marc Chavannes in 1957.1957 Borazon

Borazon, a boron nitride allotrope, is the fourth hardest substance, after aggregated diamond nanorods, ultrahard fullerite, and diamond, and the third hardest artificial material.