The Stripped Hex Screw Sets by Cal-Van Tools are available in metric (No. 439) and SAE (No. 440) sizes. These 9-pc sets are designed for removing rounded or stripped fasteners with internal drive heads, though they can be used on new screws as well. The sets feature a reverse twist in the hex key that bites into the stripped out hex for easy removal, according to the company. The sets come in a full range that removes most common sizes.