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