An air-core dry-type reactor is a customized product designed to meet specific electrical, mechanical, economical and environmental requirements. After a short overview about the history of air-core dry-type reactors design aspects the chapter explains the influence of the specified parameters on the HVDC product. All these factors influence lifetime, sound and maintenance of the equipment. Filter reactors, smoothing reactors, phase reactors, damping reactors and other reactors are the main reactors utilized in HVDC systems. Recommendations for testing, transportation, and installation of air-core dry-type reactors finish this chapter.