How thin is acupuncture needle?

Acupuncture needles are designed so thin that when they go in, they don’t cause any sensation. In fact the thickness of acupuncture needles are couple of times less than a single hair, and significantly less than a syringe needle. Also the design of acupuncture needle is different from other forms of needles: For example, syringes have a cutting edge, whereas acupuncture needles are like a wire with a handle to slide in and out of the skin with no resistance and no damage.