SKLZ PowerBase Tennis Trainer Multipurpose trainer for practicing all your tennis skills; dual-swivel connectors keep cord from tangling Builds quickness, hand-eye coordination, and stamina; 15-foot Kinetic Cord stretches up to 30 feet Sets up virtually anywhere and stores easily; cord and training balls fit into base No need for a ball machine or wall; rugged, non-slip rubber base for indoor and outdoor practice Ages 7 and up; base weighs 2.75 pounds; includes two practice tennis balls