Plastic pellets are used in the tumbling process to cushion and protect your rocks. It is mainly used as filler material in Steps 2 and 3 of a 4-step kit to make up for lost volume that occurs during the tumbling process. It is highly recommended to use plastic pellets during the Final Polish and Burnishing Steps to cushion and protect the rocks from eachother.
Plastic pellets are re-usable, but it is highly recommended to use clean pellets on each step as to not contaminate the current steps grit or polish with grit or polish from prior steps.