Which product is likely to be used for permanent styling of hair?

The product that is used for permanent styling of hair is perm solution. This is because perm solutions contain chemicals that break down the hair's protein structure. When the hair is treated with this solution and then wrapped around rods, the hair can be reshaped into curls or waves. Once the desired shape is achieved, a neutralizer is applied to restore the hair's protein structure, effectively making the style a permanent one.

While gel and hair spray are products that can help achieve temporary styles by providing hold or enhancing texture, they do not permanently change the hair's structure. A moisturizer is used to hydrate and improve the condition of hair but does not alter its shape permanently. Therefore, perm solution is specifically designed for creating long-lasting changes in hair texture, making it the correct choice for permanent styling.