TEN BUCKS!?!?! Way too much for my cheap self.
If they are solid, you could probably use them.
I have two sets of rings. One is a solid steel set (I had a welder friend make) that is attatched with 3/4" nylon rope. I have them taped up (I don't allow my students to swing on them). They are for conditioning purposes only.
The second set is my "traveling set". It was made with 1/2" rope and 2-18" pieces of THICK hose attached to each end and tied off to form a large "C". This works great for all conditioning exercises (I would NEVER do swinging type movements though). I taped these too.