Out of every standard gear used for mechanical systems, the spur gear remains the most simple and widely used. Typically, they consist of a circular gear body with straight teeth across the entirety of the circumference. They also feature parallel and coplanar shafts. Alone, spur gears can provide for rotational motion, though if paired with a gear rack, can also create linear motion. Spur gears can be produced from a variety of materials, ranging from metals to polycarbonate plastics. Due to their simplicity, spur gears are easy to design and produce, thus making them very cheap and economical for a wide range of applications.