The Allstar bolt extractor kit is a power driven drill bit and an extractor in one tool. This extremely useful tool has been specifically designed to be used with a 3/8" variable speed reversible power drill. Easily extract broken, rusted, stubborn bolts like a pro with the bolt extractor kit. No grinding or center punch required. Self centering tips work on jagged, uneven breaks. Each four piece bolt extractor kit includes 1/4" (M6), 5/16" (M8), 3/8" (M10) and 1/2" (M12) bits.