Pneumatics are machines designed to operate through gas or compressed air power. Pneumatics cover a wide range of applications, most commonly in the form of power tools, air brakes in motor vehicles, and other devices like compressors. Used across a broad spectrum of industries, pneumatics are often preferred because of their relative ease of use and low cost. Common types of pneumatic products include compressed air cylinders, available in standard and miniature sizes for varying applications, and directional control valves, which control the flow of compressed air. Directional control valves are also found in hydraulic systems and are commonly available in two-way, three-way, and four-way designs.