In reference to the design patent: USD 666,896 S1
Can a similar product be made without violating this patent? What exactly is patented? The loops? The look?
A design patent such as this one protects an ornamental design; or, roughly speaking, what something looks like. It is the entire design, not just one part of it, that matters.
A product that looks like what is shown in the design patent's drawings might infringe.
It is hard to answer any more precisely than that without knowing what the "similar product" looks like.
Design patents are more powerful than they used to be in light of recent rulings:
Do some more research and you will see also. It used to be said that a 10% difference is enough to get around a design patent ... I don't think so anymore.