This adapter has female 5.5mm x 2.1mm DC barrel jack on one end and a 2.5mm x 0.7mm male DC plug on the other end.

This is handy if you to power device with 2.5mm x 0.7mm DC jack (e.g. Odroid board) with a more common 5.5mm x 2.1mm power supply.

The overall length of this adapter is about 15.5cm.

Take note that this adapter does not do any voltage conversion. Be mindful of the voltage requirement for your device.