What are acupuncture needles made of? How big are they?

Acupuncture needles are made from surgical stainless steel, and are pre-sterilized for single use only (disposable). The needles are made in different gauges and lengths to be used on different areas of the body. The needles used are mostly very fine, and vary from 0.12 mm to 0.35 mm in diameter (about the size of a thick human hair).