Tinksky DIY 2-Way Speaker Box Terminal Binding Post Round Screw Cup Connector Subwoofer Plug (Black) Material: durable plastic, copper and gold-plated metal. Cutout diameter: about 45mm (1 78 "); Overall diameter: about 75mm (3"); Top-mount depth: 20mm (78"). Terminal cup for speaker subwoofer boxes. Gold-plated contacts for optimal signal transfer. Screw terminals ensure a tight and secure connection. Rear connections use quick disconnect connectors. Positive (Red) and negative (Black) indicators to ensure proper wiring.