Acupuncture consists of the insertion of very fine, solid stainless steel needles that are about the thickness of a human hair. They do not penetrate very deeply into the skin. Most people report feeling no discomfort whatsoever, or at most, a brief sensation upon insertion.
How many needles you'll need for your therapy depends on what your therapist is treating. In general, the number of needles range from as few as four to upward of 18. Each needle is sterilized, packaged separately, and only used one time.