In body piercing, there are four basic types of sterile piercing needles; straight needles, curved needles, I.V. Catheter (also known as Cannula) needles and internally-threaded needles. For many piercings, any of the straight needles will suffice. However, some piercings (like the tragus piercing) require curved needles. Cannula needles are very popular in Europe and are becomming more popular in the United States.
Internally-threaded needles (shown in photo) feature threads at the rear of the needle that enable the piercing jewelry to attach to the needle itself, creating a smooth, continuous piercing surface. This attachment enables the piercer to both pierce and install the initial jewelry at the same time. Once the needle is through the skin and the jewelry in place, the needle is unfastened from the jewelry, leaving the jewelry in place without further manipulation.