NRG EdisonPOLISHED HIGH TENSION SURFACES WITH HANGING SILVER PLATING SIGNIFICANTLY GREATER METAL MASS FOR OPTIMUM CLAMPING PRESSURE AND CURRENT DELIVERY BERYLLIUM COPPER BASE METAL Provides superior spring tension and long lasting, low impedance AC power connections. Typical materials such as brass, or even high purity copper aided by spring and wedge devices, simply cannot equal the unparalleled retention strength of high mass beryllium copper. INCLUDES DUPLEX