"Quick Start 36" Red Balls are 15% larger than standard tennis balls, increasing the success rate for beginning children in 10 and Under Tennis programs (and adults as well). They are specifically designed and tested for 36-foot USTA recommended courts. "Quick Start 36" Red Balls are available in both 30-ball bucket and 60-ball bucket sizes. The color-coded buckets offer both convenient and separate storage. All buckets now shipping with improved new hinge design for easier ball access and storage.