7x Drill Depth Stop Collars Dowels & 1 Hex Wrench Set for Drill Bits Consistent Drill Bit Stop Collar is mainly used for fixed limit drilling depth on the drill bit. Material: carbon steel Size: stop collar:345681012(mm) 1/8,3/16,1/4,5/16,3/8,7/16,1/2(inch) Quantity: 1pc hex shank,8pcs stop collars