Bought myself a StayBall. Really makes a difference in doing the videos with Nicole. I'm still shaky,but the ball isn't shooting across the floor!!! (It has 2# of sand in it.) That 5 minute core video means business!!! Kind of sneaks up on you. Worked out,few hours later thought,"Five minutes doesn't seem like it did anything." Well,the next day,oh OUCH!! My abs are killing me!!! Love it!!!