Lycra is the trademark name of a chemical fiber of DuPont Company in the United States. It is called spandex in China and tenter in Hong Kong and Taiwan. Spandex can stretch freely by 4 to 7 times, and soon returns to its original length after the external force is released. It is mostly used in T-shirts, underwear, swimwear and other products, which can increase the elasticity of clothes and improve human comfort. Lycra itself has no slimming function, but Lycra is added to some body-shaping underwear to increase the elasticity of the fabric.