Glass mason jars are essentially clear glass jars with a screw-on lid. John Landis Mason designed and patented the product in 1858. In the days before refrigeration, cooks used these iconic items to preserve just about everything from fruit to vegetables. Glass canning jars are available in a range of sizes and styles designed specifically for home canning. Different types of canning jars are available, with their appropriate use determined by the method being used and foods being preserved. http://www.hz-bottle.com/glass-food-jars/glass-mason-jars/