This is a standard '130 size' DC motor. It comes with a wider operating range than most toy motors: from 3 to 9VDC, This range makes them perfect for controlling with most of the Arduino Motor Shield, or with an Arduino where you are more likely to have 5 or 9V available than a high current 3V setting. They'll fit in most electronics that already have 130-size motors installed and there's two breadboard-friendly wires soldered on already for fast prototyping.