Review (4/5): Temporarily functional
I use these after climbing in order to increase blood flow to my fingers in hopes of reducing joint or tendon pain and they do work well for that. From how I understand these work, they will only relieve pain if you want more blood to flow to the area since the pressure and movement are stimulating the tissue. These don't help the knuckle as it is not a part of the thin finger but the DIP and PIP joints are greatly relaxed. I describe the sensation similar to the prongs of a fork being rolled across a finger without the fork being pushed hard into the skin. It could also be described as rubbing a ball of Christmas lights across a hand.
For the price these are reasonable quality justifying the loss one stars. They all appeared intact when they arrived however the first one I used broke immediately. A short time later a second ring broke after only being used twice. I wound not say that I stretched them beyond their limits as my fingers are quite small. The rings are somewhat made of coils of wire and could be somewhat pieced back together for further use though this takes additional effort. I was able to contact the company and they gave me a full refund so five stars for their customer support.