Ideal for adapting an existing DC Barrel Inner from 2.1mm to 2.5mm. Reuse old power supplies with new equipment. 2.1mm Inner Female Socket to 2.5mm Male Plug with 5.5mm Outer Diameter. Also available in 2.5mm to 2.1mm. 2 Year Warranty. The LINDY DC Jack Power Supply Converter Cable is designed to change your existing DC jack from 2.1mm inner to a 2.5mm inner whilst the outer remains 5.5mm. This saves time and money on new power supplies when you can reuse your existing ones.