The dog LOVES these. They are soft enough for it to get its teeth into, but can support the weight of the dog hanging off one (20kg). Great for fetch or tug of war. Having 2 rings means if the dog won't give the toy up they will drop it when you show them the second ring.
Our dog is a real chewer and it still took about a year to destroy the last set, but we didn't leave it out as a chew toy.

We have a puppy with a damaged leg and too much energy right but the pullers have been great in expending some energy and keeping her amused. Looking forward to her really getting to run after them when the leg is healed.

Great chase toy. Direction of roll can be changed by the angle you throw it.
I suspect it won't last long if used regularly as a tug toy. The material doesn't appear to be holding up too well to big teeth.