The GoFit(R) Core Ab Ball offers a fun and challenging way to stretch, tone and tighten your core. The round, unstable surface allows you to train both the primary muscle groups along with the smaller stabilizing muscles. The included Core Ab Ball DVD features nationally-acclaimed fitness instructor, Brook Benten, who leads you through the ultimate 22-minute core workout chapter to maximize the time you spend strengthening your core. FEATURES: Ab stability ball for core strength training Round, unstable surface for targeting specific muscle groups Included Core Ab Ball DVD hosted by Brook Benten Included inflation tube 20cm diameter Manufacturer's 90 Day Warranty Model: GF-20BALL