CHANZON UL Wire 9V Battery I-Type Power Supply with Center Positive 2.1mm x 5.5mm Male DC Connector Holder Clip Converter (5 Pack)
A 5-pack of UL-certified 9V battery connector clips with a 2.1mm x 5.5mm male DC barrel output, designed to help you power Arduino, LED projects, and other 9V-based builds from a standard 9V battery. The main caveat is polarity and compatibility: these are center positive, so they may not work with devices expecting center negative.