Futons are based on the original Japanese style mattress, however western style futons have several differences, they are often and are always much thicker and larger than Japanese futons and are placed on frames for dual use as a  Chair bed (Single size)or Futon Sofa bed (Double size). They are usually filled with several layers of either, wool cotton and man made fibers and sometimes have a foam core.

Futon sofa beds are great alternative to a bed if space is at a premium and are often sold with different  frame types,  i.e. classic pine frame,  hard wood frames or metal frames some with sprung slats on the base for extra comfort, most frames are sold including the mattress.