Tonsiki 3 Pcs 1/4 Inch Hex Shank Screwdriver Bit Holder 2", 4", 6" Extension Set for Screws, Nuts, and Any Drill and Handheld Driver Hex Shank: 1/4" hex shank (6.35mm). Length: 2"(60mm),4"(100)mm,6"(150mm). Perfect for drill, screwdriver, batch head and other to transfer. Interface has a locking mechanism, built-have magnetic, automatically pop up batch head. Extend all kinds of screwdriver bits, screwdriver head conversion uses.