I just had sample orders of 3 types of rings come in. I’m delighted with the wood and steel tubing ones, which are 230mm/9″ in diameter like my trademark ring. You can see them here with fuller descriptions. However, you won’t see the ABS ones listed in my rope shop as shibari rings as they are not, in my opinion, fit for that purpose, albeit great for their intended use as gym rings. A shame as the idea was great in theory.
Unfortunately, only after I had ordered the ABS ring samples, I was given the heads-up about this material not good with friction as the heat build up causes it to melt. I was praying these would be made of a grade of ABS with better heat resistance. A quick test involving drawing a rope under tension over a sample showed this not to be the case. A few pulls using Hempex quickly generated that familiar burning plastic smell and left black streaks on the rope. Even after a few passes, damage was obvious.
Unlike wood, where once a couple of initial indentations appear things settle down, the friction damage is cumulative. Whilst I see no immediate danger of unexpected failure, constant lifts could start to saw through this material. At first it would create a rough and uneven surface, which could abrade rope, but eventually severe damage might occur to the ring itself. Such rings *could* be used if all your lifts are gentle, you don’t expect it to last as long as wood or steel and you meticulously maintain the wear surfaces to avoid roughness or excessive material depletion.
It goes to show that not everything that looks suitable is suitable and cheap solutions often give you what you pay for.