Stainless-steel filiform needle The everyday choice. High tensile strength and springiness keep the shaft straight and mirror-smooth; it survives autoclave heat, resists rust and clinic chemicals, so it is used everywhere from ear points to deep gluteal muscles.
Gold & silver needles Far better electrical and thermal conductivity, but the shafts must be made thicker to compensate for lower mechanical strength. The high price restricts them to special applications such as low-frequency electro-acupuncture or heat-tonifying techniques.
Iron and plain-carbon steel needles These rust quickly, lose elasticity, and can snap. Apart from an occasional appearance in magnetic-needle protocols, they have been largely abandoned.
