You've never seen a solar bag like this! Our 50-foot-long, 3-foot-diameter, thin, black plastic solar bag holds over 200 cubic feet of air. Simply fill with air by running, tie off the ends, and let the solar energy of the sun heat the air inside the bag. Within about five minutes, the bag (which must be tethered with string) will rise into the sky. Absolutely amazing to see and teaches many scientific principles such as density and buoyancy.These solar bags are the largest on the market anywhere. Your students won't believe how big it is!