Which of the following is NOT part of a pin curl?

The correct answer is length, as it is not a recognized component of a pin curl. Pin curls are typically composed of three main parts: the base, the curl, and the stem.

The base is the section of hair that is closest to the scalp and is stationary; it provides the foundation for the curl. The curl itself is the actual rotating part of the pin curl, which defines the shape and bounce of the curl. The stem is the section of hair between the base and the curl, providing flexibility and movement to the curl.

Since "length" does not correspond to any of these components in the context of pin curls, it is not considered a part of the pin curl structure. Understanding these elements is crucial for hairstyling, especially in techniques involving curls and waves.