What type of rods are used in permanent waves that maintain their shape?

The correct answer is the type of rods that are typically referred to as straight rods. These rods are designed to create a consistent curl pattern that maintains a uniform shape throughout the permanent wave process. Straight rods provide a well-defined curl, allowing the hair to wrap around the rod evenly, which is essential for achieving a balanced and lasting wave.

Straight rods are commonly used because they support the integrity of the curl and help deliver a consistent result in texture. Their design facilitates even tension around the hair, leading to a predictable curl formation upon the completion of the perming process.

Other rod types such as curly rods, flexible rods, and curlers each have their unique uses and results when perming hair, but they may not offer the same level of uniformity and curl definition that straight rods do. Curly rods may create tighter curls, while flexible rods allow for different curl styles but can result in uneven tension. Understanding the characteristics of each rod type and their influence on the perm outcome is crucial in cosmetology.