DO NOT BUY THIS TERRIBLE PRODUCT!!
I rate it a one, because there isn't a zero. I bought it two weeks ago and one of the thick rubber bands already has snapped. Luckily, I was going slow on it due to me being new to using it, so no injuries. This is an awful device. Do not waste money, like I did. Now, I find out there is no refund unless specific conditions are met. TERRIBLE TERRIBLE PRODUCT!!!