with 8 different diameter turning holes, simply loosen the screw, rotate the red tool holder to the desired size, and then retighten to easily adjust the diameter.

Φ1/2

Φ3/4

Φ3/8

Φ5/8

Φ5/16

Φ7/16

Φ9/16

Φ11/16

Durable Aluminum Alloy