Story time. Although I had real rollers as a kid, I got the idea to make my own. Dad was a steel salesman, and sold to the many small factories in central Ohio, including one that made industrial rollers. He got me a set of 4" wide x 3" rollers and the steel beams to go with them. All I needed to do was bolt them together and make a belt, which I did. Two people could ride them at once. Super loud--like a jet taking off, but fun at roller parties. Wish I'd taken a pic.