Tom's Tumbler Inserts are made of corrugate plastic, sized to fit perfectly inside the net of the Tumbler it made for. These slide inside the net and over the axle to make a secure divider in the mesh chamber. It slides on the axle so you can make your chamber half as large, 1/3 as big, etc. This is a great solution when you are getting to the end of your tumbling and have a smaller than needed batch to trim. Or if you are only processing a small amount.
Note: Tom does not recommend tumbling with less than 3/4 of a pound, no matter the size of the chamber. The tumble trimming process needs the weight of the buds as well as the mesh chamber.