Cotton string(s) dipped in a black powder slurry, allowed to dry, then wrapped in light Kraft or rice paper. Depending on the fuse (or match), it will burn at a rate of about 1 foot in 3 to 5 seconds (depending on the slurry - sometimes faster, sometimes slower) if unconfined. However, because the burn has been confined in the paper, it develops a pressure wave which travels between 30 and 60 feet per second. The name is very descriptive of the product. (This is also classified as a Class B product.)