DC Barrel Jack 2.1mm – Panel Mount DC Barrel connectors are commonly used as power connectors. This barrel jack is center positive with a center diameter of 2.1mm. Specifications: 2.1mm x 5.5mm metal DC power pack panel mount Pin/Jack Diameter: 2.1mm Panel Cutout: 8mm (0.31″) Maximum Panel Thickness: 2.1mm (0.08″) Category: Power Connectors