The interior cleaning brush is a handheld scrubbing tool designed for upholstery. For leather seats, it uses soft horsehair bristles to gently agitated dirt out of the leather’s pores without scratching the finish. For fabric seats and carpets, stiffer nylon versions are used to pull out deep-seated dust and hair. Using a brush is far more effective than just wiping with a cloth because the bristles create a lather with the cleaning chemical, lifting stains to the surface.