If I was to be looking to buy a tumbler today, it would be the Harbor Freight dual tumbler, mainly because it seems that they don't offer the single barrel now and the price is right. For $69.99, the dual should be a bargain. My single barrel has had so many tumbling hours on it, it's crazy. Still works perfectly. Aquarium gravel, tot lot gravel, driveway gravel, all work. I just use a several drops of dish washing liquid and enough water to cover the contents, and let it run. Don't overfill the barrel. The instructions are pretty clear about weight. I wonder though if the second barrel might load the motor. Good luck!