The Delta IV family includes three classes of vehicles. The medium-class vehicle has a Common Booster Core and a 4-meter-diameter upper stage and payload fairing. The medium-plus has two basic versions: one with a 4-meter-diameter upper stage and payload fairing and two solid motors, and one with a 5-meter-diameter upper stage and fairing and two or four solid motors. The heavy-lift vehicle consists of three cores strapped together.