I just received bands yesterday, and I was just testing out the feel of the green and black bands together and after 4 curls...the metal part of the green band popped out of the connecting socket and snapped into my foot.  Thanks to the poor quality of this product, I now have a giant welt on my foot. Just to let everyone know I am 5'11 and 160lb, by no means a BIG guy, and was not even close to pulling with full force. Perhaps I just received a lemon, but I'm demanding a refund. I would advise any potential buyers to be careful.