3.5mm / 1.1mm to 5.5mm / 2.1mm DC Jack Adapter

This convenient 3.5mm/1.1mm or 5.5mm/2.1mm DC Jack adapter 

2.1mm inner diameter (5.5mm outer diameter) is the most common type of DC plug, but you can use this adapter for anything else that has a 1.1mm ID (3.5 OD) DC jack! 

Push the adapter in all the way, and you'll feel a satisfying click to know it's seated.