The OnCourt OffCourt Jingle Bell Red Foam Training Tennis Balls are softball-size foam balls, with an internal bell that rings when it strikes any surface or the racquet. These fun balls are ideal for beginning players on 36-foot courts in 10 and Under Tennis programs. Jingles are made from 100% density top-of-the-line foam balls, designed for durability and consistent bounce. They also rebound to an appropriate height for the youngest of players.Features:Set of 6 red foam tennis ballsSoftball sizedInternal bellThe OnCourt OffCourt Jingle Bell Red Foam Training Tennis Balls allow ground-breaking training aid for sight-impaired tennis players. The bell inside makes playing fun while helping with tracking and rhythm skill-building.