Mixtures of ceramic shapes are the latest thing in rock tumbling! They do four things really well. (1) they act as a cushion (just like plastic pellets) but they are also hard, so (2) the Silicon Carbide grit does not embed in the shapes and thus, the shapes can move through the stages right along with your rocks; (3) they are perfect to make up lost volume due to the abrasion process, and finally (4) they carry the slurry to every part of every rock to create a perfect "balanced load". Now, even if you have only one or two rocks (or pre-formed shapes) in the tumbler, simply make up the proper volume with shapes and watch the rocks shine! This is a 1.5 pound mixture of hard, nonabrasive ceramic shapes, at $8.31/Lb, in a 1-pint plastic container.