DeFelsko HHDFANBRSH Fan Brush Electrode 152 mm (6”). The DeFelsko PosiTest HHD Electrodes include various options, such as flat brush, fan brush, conductive paddle, and rolling spring coil electrodes to best fit a wide variety of testing needs. Each Rolling Spring Coil Electrode includes 2 pre-installed spring couplers and requires the purchase of a spring connector to attach them to the PosiTest HHD. Electrodes and brushes are made of stainless steel.