Hair curlers are styling tools used to create curls or waves in the hair. They come in a variety of shapes and sizes, and can be heated or non-heated. IRONS, which are five letters long, are heated tools that use heat to shape the hair into curls. Perms, also five letters long, are chemical treatments that permanently change the structure of the hair to create curls. Rollers, seven letters long, are non-heated tools that use tension to shape the hair into curls.