✔ 2.1mm x 5.5mm plugs are commonly used for 5v, 9v, 12v, 15v and 24v power adapter. However, all such power adapter uses 2.1mm x 5.5mm barrel plug. 20ft power extension cable for universal 12V DC power adapter, or device and For any applications that requires DC input and accept 2.1mm x 5.5mm plug,female to male connector.
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