In the Pony Swing business you will find sellers that use steel-belted tires to make their swings. When you cut into a steel belted tire, there are hundreds of tiny, razor-sharp steel threads that poke out of the tires. Now, these people will tell you that they "coat" or "cover" the edges of the swings for safety. We've seen these type of swings, and they don't measure up to our safety specs. This is why we use ONLY nylon tires...meaning there is NO steel at all in our tires.