Mounted Bristle Brush with stiff horse hair bristles in a end shape has a 3/16" head dia. and 2/4" trim length, 3/32" shank, Style A-MB3. Made in USA. 25000 RPM Max Speed. Bristle Brushes are used to clean and prepare surfaces for buffing and polishing. They are made with natural animal hair horsehair for stiff and goat hair for soft bristles. Bristles are securely held in steel rings evenly distributed and trimmed. The wheel cup and end shapes will work on flat curved hard-to-reach surfaces.