For centuries burning glasses like this were used to start fires. The oldest existing burning glass (known as the Assyrian Nimrud Lens) was found in Iraq, dating back to the 8th century BC. During the 18th century, they were some of the many items traded to the Natives. In 1752, Benjamin Franklin wrote his friend, William Strahan, to buy and ship him a large burning glass "of about 12 inches Diameter."  And in 1774 the French scientist Antoine Laurent Lavoisier used a huge burning glass to discover oxygen, which ended the belief in the five elements that compose the world. Our lenses are made of glass with a 6-power optic and measure 2 inches in diameter. It comes with a cloth carrying bag and 10 pieces of char cloth measuring approximately 2 in x 2 in.  *Tin not included.