Ultimate Series 24K Gold Plated Beryllium Red Copper Banana Plug 12-18 AWG Gauge Size 4Mm Connector for Speakers Wire Amplifiers Hi-Fi Sound Systems (24 Pcs (12-Pairs), Banana Plugs). The entire core from the bottom up to the tip is made of beryllium-red copper for better sound optimisation and longer lasting use especially if you are changing the connections frequently.