Hair roller
![model Emily Ratajkowski in hair rollers with photographer Tony Kelly](/Images/godic/202501/16/Emily_Ratajkowski_in_hair_rollers_with_Tony_Kelly_for_2013_GQ_Türkiye_photo_shoot2447.png")
![](/Images/godic/202501/16/-Emily_Ratajkowski_having_hair_roller_removed_for_2013_GQ_Türkiye_photo_shoot.ogg2447.jpg")
![Three hair rollers of different diameters.](/Images/godic/202501/16/Curler_20052448.jpg")
A hair roller or hair curler is a small tube that is rolled into a person's hair in order to curl it, or to straighten curly hair, making a new hairstyle.
The diameter of a roller varies from approximately 0.8 inches (20 mm) to 1.5 inches (38 mm). The hair is heated, and the rollers strain and break the hydrogen bonds of each hair's cortex, which causes the hair to curl. The hydrogen bonds reform after the hair is moistened.