What kind of needles are used in acupuncture?

Acupuncture needles are extremely fine, sterile, solid, and flexible filiform needles. They have a very small diameter, typically ranging from 0.16 millimeters (0.006 inches) to 0.30 millimeters (0.012 inches), which is thinner than a human hair. These needles are often made from surgical stainless steel, but can also be made from other materials such as gold, silver, or titanium. They are typically between 1 to 3 inches in length, and have rounded or blunt tips to minimize tissue damage during insertion.