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

It is handy if you have 5V DC power supply with a barrel plug and you want to power a Type C USB device (like a Raspberry Pi 4).

Take note that this adapter does not do any voltage conversion. Most, if not all USB powered devices runs on 5V, be mindful of the voltage that you connect to the barrel jack.

Disclaimer:

Use at your own risk. Always check your voltage with a voltmeter and make sure your device can handle the power that you are connecting it to!