So I was hesitant to buy all 3, since it is quite a bit of money. But once I got it I quickly realized that it was worth every penny. As soon as I opened the box, I alternates between the smallest two wheels for about 5-20 minutes. My back loosened up and actually cracked quite a bit! Doesn’t sound like a big deal, but that’s the loosest it’s been and the first time it really cracked in months!!! I had to take one star away though because I paid for 10 day shipping, and it took 3 weeks to get to me!! I don’t understand why it took so long. It wasn’t international or an APO. It was being sent to a US address. Oh well. I’m just glad I finally got it.