Made of hard-anodized aluminum, each collet fits into a recess drilled into the work, and expands to hold it when you tighten the screw in the back of the shaft
The collets also allow stock to be removed and remounted with repeatable concentricity – important for sanding and finishing a workpiece
Sizes available are 1/2" to 1 1/4" in 1/8" increments and 1 1/2"