Which diameter size means the area between partings is exactly the same as the diameter of the roller?

The choice indicating that the diameter size means the area between partings is exactly the same as the diameter of the roller is indeed the correct approach. When referring to a 1x roller diameter, this implies that the width of the section of hair being rolled or parted is equivalent to the diameter of the roller itself. This means that each parting is equal to one diameter of the roller, ensuring consistent tension and curl formation throughout the hair.

In contrast, options like 2x or 3x would imply that the area between partings is larger than the diameter of the roller, thus creating greater spacing that could lead to variations in the final curl effect. A half-inch option would denote a specific measurement that does not correspond to the relationship being asked about. Understanding this relationship between roller size and parting is essential for achieving uniform results in hairstyling techniques.