These are okay but they are fairly stiff and do not stretch easily. I guess there are no ratings for that - they could range from a light rubber band to nearly solid plastic. I have had softer-stretchier that were more comfortable. They are well made with no edges from molding.
An utterly horrible product; no stretch at all, zero. Very hard, rough plastic. Has sharp edges from the molding process. Just a dreadful excuse for a C ring.