One Each Nylon, Blue Nylon and Bronze. Otis' All Purpose Receiver Brushes allow you to choose the right brush for the right project. These brushes are the elite in cleaning those hard to reach places. They give you the ability to scrub places where carbon, powder, and copper residue hibernate. These brushes are available in a variety of different tolerances. The softest is the nylon bristled brush, followed by a slightly more aggressive blue nylon bristled brush. The most aggressive of Otis' All Purpose Receiver Brushes is the bronze bristled brush.