NUOLUX 10 Pairs of 4mm Gold Plated Banana Plug Connectors (Black+Red) Color: Black, red. Material: Durable metal and ABS. Size: 4mm. Double screws locking, without crimping or soldering. Widely used to ensure a tighter connection of a speaker wire to the binding post in the back of the speaker or in the back of the audio receiver. Create your own high quality charger adapters with these gold plated 4mm banana plug connectors. The screw on the side physically secures the wire in the adapter while also ensuring electrical conductivity without the need to solder.