A banana connector (commonly banana plug for the male, banana socket or banana jack for the female) is a single-wire (one conductor) electrical connector used for joining wires to equipment. The term 4 mm connector is also used, especially in Europe, although not all banana connectors will mate with 4 mm parts, and 2 mm banana connectors exist.
Various styles of banana plug contacts exist, all based on the concept of spring metal applying outward force into the unsprung cylindrical jack to produce a snug fit with good electrical conductivity. Common types include: a solid pin split lengthwise and splayed slightly, a tip of four leaf springs, a cylinder with a single leaf spring on one side, a bundle of stiff wire, a central pin surrounded by a multiple-slit cylinder with a central bulge, or simple sheet spring metal rolled into a nearly complete cylinder.
The plugs are frequently used to terminate patch cords for electronic test equipment, while sheathed banana plugs are common on multimeter probe leads.

Banana Plug FEV-C166

Banana Plug FEV-C166

Banana Plug FEV-C167

Banana Plug FEV-C167

Banana Plug FEV-C168

Banana Plug FEV-C168

BANANA PLUG FEV-C169

BANANA PLUG FEV-C169

BANANA PLUG 2MM MALE FEV-C171

BANANA PLUG 2MM MALE FEV-C171

4mm male banana plug FEV-C172

4mm male banana plug FEV-C172

4mm stackable banana plug connector FEV-C173

4mm stackable banana plug connector FEV-C173

4mm Metal Banana Plug Zinc Alloy Nickel FEV-C174

4mm Metal Banana Plug Zinc Alloy Nickel FEV-C174