What is the full inflation size of the p.ball? April 05, 2019 19:13 Updated The full inflation size of the P.ball is 19.5" - 20.5" in circumference. Related articles What is the p.band? How can I stream/cast the workouts to my TV? How is P.volve different from Barre? What is the p.ball? Is there a student or teacher discount?