The colorful envelope is usually made of nylon or polyester, the same type of cloth that parachutes are made of. It is very tightly woven and is coated with a material that makes it very air tight. The nylon is only used to keep the hot air in the balloon. The basket load is transferred by steel or Kevlar cables to a series of vertical load tapes which carry the load. Balloons range in size from about 54,000 cubic feet for a one- or two-person balloon to over 250,000 cubic feet for a balloon capable of carrying a pilot plus eight or ten passengers.