PIXNOR 5pcs DIY Home Car Stereo 2-Way Speaker Box Terminal Binding Post Round Spring Cup Connectors Subwoofer Plugs (Black) Color: mainly black. Material: durable plastic, copper and gold-plated metal. Cutout diameter: about 45mm (1 7/8 "); Overall diameter: about 75mm (3"); Top-mount depth: 20mm (7/8"). Terminal cup for speaker subwoofer boxes. Gold-plated contacts for optimal signal transfer. Screw type terminals ensure a tight and secure connection. Rear connections use quick disconnect connectors. Positive (Red) and negative (Black) indicators to ensure proper wiring.