OMNIHILAdapter Plug Converter 5.5 millimeters x 2.1 millimeters Female Plug to 5.5 millimeters x 2.5 millimeters Male Plug

Simple and it works.

Used for my 2.1mm power supply to plug into a few DAC amps that take a 2.5mm

Got me out of a bind that the original vendor put me in.

solid build quality. connects a 2.1mm male into a 2.5mm female. I used this to bridge a charging cable into my power pack battery

Exactly as advertised to adapt a 5.5 mm x 2.1 mm power connector to a 5.5 mm x 2.5 mm connector. Seem to be well made. Only negative is rather pricey at nearly $9 for this small item.

Works great. I think it is a little on the expensive side, but it worked perfectly. It fit my Phillips Hue bridge with no issues.

For those of you who are trying to mate a Belkin Battery Backup unit to an ATT BGW210-700 Router, here is what you need to know. The Belkin has a 5.5mm X 2.1mm plug. The BGW210 accepts a 6.3 X 3.0mm plug. As far as I can tell, this seller does not have that size adapter. So do a search on Amazon for LANMU usb to dc. An assortment of plugs contains the one you need. I give this seller 5 stars for an easy return.

Using this to use 3rd party power supplies with HX Stomp. This one plug lets you use a OneStop, BOSS, or other standard 9V pedal power supply with an HX STomp (Assuming you can give 1000mA to it) without special cables.