2 Pack USB DC 5V to DC 9 Volt USB Power Supply Cable, Max Current 800mAh, Tip Negative Connector, Compatible for Guitar Effects Pedals Power Supply Adapter
Plug & Play, it is really handy when travelling or outdoors, just power it with a 5V power bank and you can start running your 9V Guitar Effects Pedals.
DC Output: 9.0V; Max Current: 800mAh; USB Input: 5V
Connector Size: Tip negative(-) design, DC Jack 5.5 x 2.1mm
Safe & Reliable, with built-in upgraded intelligent IC circuit, our voltage adapter provides your devices perfect protecetion from over-current, over voltage, overload or short circuit.
Could work for most brands of guitar effect pedals (center negative) also be used to power (tip negative) keyboards.