8 Pcs Bit Limit Ring 3mm 4mm 5mm 6mm 8mm 10mm 12mm 16mm Drill Stop Assortment for Drill Bits Consistent Drilling Material:Carbon Steel Mainly for fixing the drill bit,limited the depth of drill holes,make depth of the hole consistent Use on twist drill bits or brad point drills to prevent excessive drill bit penetration Each drill stop is finished with a black oxide finish and constructed of cold rolled steel Package include:8 pcs Drill Ring,1 pc Hex Wrench