For under $20 bucks you can have some serious fun. Well at least I thought it was serious fun. The "solar bag" is basically a very light weight black plastic material. You simply fill the bag up by running, tie off the ends, and let the sun do the rest. The sun heats the air in the solar bag causing it to float like it is filled with helium, even though it isn't. You can buy multiple bags and tie them together to look like UFO's or letters. Still don't get it, video after the break.