The Universal Rocket or UR family of missiles and carrier rockets is a Russian, previously Soviet rocket family. Intended to allow the same technology to be used in all Soviet rockets, the UR is produced by the Khrunichev State Research and Production Space Center. Several variants were originally planned, of which only three flew, and only two of which entered service. In addition, the cancelled UR-500 ICBM formed the basis for the Proton carrier rocket.