Mini Ball, Small Exercise Ball for Yoga,

Small therapy ball strengthens key muscles in the abdomen, enhances core health, and improves endurance, posture, and balance when used in rehabilitation, strengthening, and toning exercise programs
Place small pilates ball under lower back when performing crunches and other ab workouts to create a more challenging and intense abdominal exercise routine
Position soft ball between your body and the floor or wall to improve stability, balance, and muscle endurance, especially when used in a shoulder strengthening or core strengthening program