SPRI Balance Trainer Sport - Dome Shape Half-Exercise Ball with Non-Skid Base - for Balance Training, Strength Building, Toning, and Improved Flexibility - 50cm Diameter, Balance Boards - Amazon Canada
How Well-Rounded is Your Stability Ball Workout? - SPRI
SPRI Exercise Balls for sale | eBay
55cm SPRI Stability Ball | SCW Fitness Education Store