Jillian Michaels 55 cm Anti-Burst Stayball Anti-burst exercise ball measuring 55cm in diameter Strengthens core, tones muscles, and improves balance Tough latex-free construction supports intense workouts Textured surface increases stability; 250-pound capacity For people between 5' and 5' 5"; includes exercise chart and pump Textured Surface Anti-Burst Exercise Chart Included For Heights 5'-5'-5"