There are 4 basic types of hair fibers. Allure, Mod acrylic or kenekalon fibers are non-natural fibers. The hair is preprogrammed and the style returns upon washing. HD or Heat Defiant are still a non-natural fiber but allows a curling or flat iron to be used with a low heat setting. Kenekalon fiber with human hair blend behaves much like the HD but has a more realistic look, feel and movement. Finally, there is human hair. Not all are equal. You may alter the styles with heat, color or chemical processes but it depends of the hair quality and type.