In ancient times, acupuncture needles were made of stone, bamboo or bone, and usually bigger (see model) than the modern ones which are small and thin with thickness of a piece of human hair and made of stainless steel for flexibility and rust prevention. Acupuncture needles of varying length and size are available and they are sterilized, and pre-packaged usually for single use. There are also reusable ones that require sterilization between uses. The needles are applied to specific acupuncture points located along different meridians on the body to treat different diseases.