If you need 5V voltage (with max 3A current) in your project and you only have 9-12V power source, this small module will solve that problem for you. It can be easily soldered to protoboard and it's only 17.2x22.2 mm small.
Step down DC-DC module with input voltage 4~35V, and fixed 5V output voltage, output current max 3A, 92% efficiency, 150 KHz switching frequency, dimensions 43x21x14 mm.