Tonsiki 8 Pieces Drill Stop Assortment Drill Depth Stop Collars Limit Ring Dowel Shaft Chuck Positioner Locator for Drill Bits Consistent Drilling Sizes:3/25,4/25,1/5,6/25,3/10,2/5,1/2,3/5 inch(3,4, 5,6,8,10,12,16 mm) Drill Bit Stop Collar is mainly used for fixed limit drilling depth on the drill bit. This drill stop assortment set includes allen wrench for tightening stops' set screws. Works with both standard and brad-point bits,setscrew type collar will not damage bits. Carbon Steel stops for durable performance.