I guess I should make some detail pics. The ring only holds the upper rollers and the rollers ride right on the upper lip of the plastic drum. Since the rollers had rubber a circular depression in them they tracked perfectly on that lip of the drum without messing up the plastic. It was one of those things I wasn't sure would work but when I tried it under "armstrong" power it worked out. The lower rollers are really the ones that carry the weight and the uppers are just more for stability. That's why the 3/4" pipe crossmember on the bottom that the bottom rollers bolt through. The ring is bolted to that. The uppers help keep all 4 rollers in their grooves on the rim of the plastic barrel as the barrel was not perfectly round and the whole thing flexes as it rolls. I know it seems hard to believe that plastic drum with all the holes in it would be strong enough to hold up rock and dirt and actually stand up over time but I assure you it has done the job much to my surprise. And way faster and with the plastic tarp on it, very little dust.