Improve your students' attention, concentration, posture, balance, coordination and more, while strengthening their core muscles. Choose from UltraFit™ Stability Balls (supports up to 220 lb) or UltraFit™ Anti-Burst Stability Balls (supports up to 2,200 lb) for increased safety and support. Pack includes 24 Rainbow® Stability Balls for students (55 cm/22" dia), 1 Blue Stability Ball for the teacher (65 cm/26" dia), and 24 Rainbow® Foam Rings (10" dia) to keep stored balls from rolling.