Magnets on the hex nut hold the reamer in place in your tool and prevent it from accidentally falling when not in the square-drive impact wrench socket. Also known as bridge reamers, car reamers, and aligning reamers, they ream, true, enlarge, align, and debur holes. All have tapered ends for easy entry into misaligned holes. Do not use for reaming tapered holes.

Reamers with helical-spiral flutes create a fine finish and reduce the chance of breakage because they move chips forward, which prevents the chips from packing into the flutes.