(Sizes: #1) 1/8"-1/4"/M3-M6, #2) 1/4"- 5/16"/M6-M8, #3) 5/16"-7/16"/M8-M11, #4) 7/16"-9/16"/M11-M14, #5) 9/16"-3/4"/M14-M18. High Carbon Alloy Tempered Steel, Multi-Fluted Extract a wide variety of screws, easy to use Hardened for long life, Reverse Thread, locks on and backs out broken studs.