What type of curl is suitable for curly hairstyles without much volume, and can be used on any part of the head?

The suitable type of curl for achieving curly hairstyles with minimal volume is square base pin curls. This method is specifically designed to create more defined curls that can lie flatter against the head, making them ideal for styles that require less bulk.

Square base pin curls help in maintaining the curl's shape and direction without adding unnecessary volume, allowing for sleek and smooth hairstyles. They can be positioned anywhere on the head, making them versatile for various looks.

The other options involve different base shapes which typically create varying curl sizes and volumes. Triangular base pin curls tend to produce a more textured look, while rectangular base pin curls focus on creating volume. Voluminous pin curls, as the name suggests, are primarily for adding significant lift and fullness to the hair. Therefore, square base pin curls are the most suitable choice for creating a controlled, curly style without excess volume.