Ultra Clean Holdings, Inc., together with its subsidiaries, engages in the design, development, engineering, manufacture, and sale of critical modules and subsystems primarily to original equipment manufacturers in semiconductor capital equipment, flat panel, medical, energy, and research industries. It offers gas delivery systems that control the flow, pressure, sequencing, and mixing of specialty gases into and out of the reaction chambers of semiconductor manufacturing tools; chemical mechanical planarization modules; chemical delivery modules, which deliver gases and reactive chemicals from a centralized subsystem to the reaction chamber; and top-plate assemblies that form the top portion of the reaction chamber. The company also provides frame assemblies that form the support structure to which other assemblies are attached and include pneumatic harnesses and cables that connect other critical subsystems together; process modules, which are subsystems of semiconductor manufacturing tools that process integrated circuits onto wafers; and other high level assemblies for use in semiconductor manufacturing, research, flat panel, energy, and medical equipment industries. It sells its products through its direct sales force primarily in North America, Asia, and Europe. Ultra Clean Holding, Inc. was founded in 1991 and is headquartered in Hayward, California.