HDF Sensor Brushâ„¢ As an extra replacement brush for use with the Arctic Butterfly ® the high-density fiber Sensor Brushâ„¢ has been designed for extreme dusting. With its high density fiber construction, this new accessory has twice the amount of fibers then the original Arctic Butterfly ® attachment brush. The HDF Sensor Brushâ„¢ is best used in excessively dusty situations. Includes a convenient carrying case for safe.