Leegol Electric Rotary Rock Tumbler Double Drum 6LB ...
The drum expands, the bottom pushes out--and the space that contains the drum is so tight that it seizes up and stops tumbling. An all-steel drum might work with this design, but not a rubber one. Note the warranty: there isn't one. If you buy it, you're stuck. I'd gladly return it, but I can't.