In one or more embodiments, the first and second fan structures may have different sizes, the first blades of the first fan structure may have sizes and/or be at angles that are the same and/or different than the sizes and/or angles of the second blades of the second fan structure. For example, flow of fluid may be more or less restricted on one side of the brake system than the other (e.g., by a spacer ring, or other component that may deprive or restrict the flow of fluid more than the other side of the brake system).