Kalevel 2pcs DIY Home Car Stereo 2-way Speaker Box Terminal Round Spring Cup Connector Binding Post Banana Jack and Plugs Subwoofer Plugs 75mm (Black) Pack of 2pcs speaker terminal spring cup connectors Material: durable plastic, copper and gold-plated metal. Spring terminals ensure a tight and secure connection. Overall diameter: about 75mm (3"); Cutout diameter: about 45mm (1.8 ");Top-mount depth: 20mm (0.8"). Rear connections use quick disconnect connectors. Positive (Red) and negative (Black) indicators to ensure proper wiring.