Mitters are ribbon-like components that suspend cloth strips or sheets over the tunnel while utilizing motion to increase friction against the car's surface. The friction zone may also include specialized front grill and rear brushes. Older automatic washes - a majority of which were built prior to 1980 - used to use brushes with soft nylon bristles, which tended to leave a nylon deposit in the shape of a bristle, called brush marks, on the vehicle's paint. Many newer facilities use either a soft cloth or a closed-cell foam brush, which does not hold dirt or water, thus is far less likely to harm any painted finish.