Acupuncture needles are very fine - approximately the thickness of a human hair - and have a flexible shaft. They are made from the finest quality surgical stainless steel, and are pre-sterilized and discarded after each use. They bear no resemblance to hypodermic syringes. 
During treatment, Classical Acupuncturists use very few needles, in order to interfere as little as possible with the movement of life energy. The average number of needles used in a single treatment is six. 
When a needle is inserted at a meridian point, a very slight prick is felt. When the needle contacts the qi in the meridian, the patient may feel various sensations. Descriptions range from sharp to tickling, from a warm breeze to an electric current. The sensation varies from patient to patient, from day to day, and from one meridian point to another. Often the patient feels other sensations such as a sense of calmness and inner well being, sudden clarity of vision, or the surfacing of an emotion or memory.