The first acupuncture needles were made of stone
We now know acupuncture needles as thin, disposable metal items, but they weren’t always around in this form. While metalwork dates back to 4500 BC in some areas of China, medical tools weren’t the top priority of ancient artisans. Small tools and decorative items such as earrings make up the vast majority of metalwork from before 2000 BC; other pieces like axes and musical instruments came later.
The first acupuncture needles were instead made of a stone called “bian”, and date back to 1700 BC. They appear similar to tools used for tattooing, bloodletting, piercing and abscess draining, so it’s possible that they evolved from these items. Perhaps stone was more readily available, or its familiarity made manufacturing needles correctly much easier.
Later on, needles made from ceramic, animal bones and sometimes bamboo appeared. Bronze needles date back to 800 BC, while the Han dynasty introduced gold needles to the world in around 200 BC. By the Han dynasty, several types of needles had been developed, and were described as long, short, sharp or dull. They were first listed as the Nine Needles in the Huang Di Nei Jing (Yellow Emperor’s Inner Classic), written during the second century BC.
These early needles were also a lot thicker than we’re now used to. Modern production techniques now give us the ability to standardise needles to lengths of 13 to 130mm (1.3 to 13 centimetres), and thicknesses of 0.16 to 0.46mm. Different sizes assist us with different applications and comfort levels of our clients; standardisation is essential to ensure quality and safety.
Source: https://www.researchgate.net/publication/303933910_THE_HISTORY_OF_ACUPUNCTURE_NEEDLES
https://www.ncbi.nlm.nih.gov/pubmed/9395637/
http://www.kaogu.cn/en/Chinese%20Archaeology/3/A%20Discussion%20on%20Early%20Metals%20and%20the%20Origins%20of%20Bronze%20Casting%20in%20China.pdf