This cable is a 5.5X2.1mm to 3.5 mm power convertion cable for guitar effects pedal with monolithic interface plug. It will convert 5.5mm*2.1mm to 3.5mm.
Length:around 7 inch.
Can be used for 9V 5.5mm (2.1mm) negative power supply.
Please note that this is an Anti-Polar cable.