For drilling wider holes in ferrous and non-ferrous metal, these bits feature a hollow core and a cutting edge on the tip circumference. The cutting surface on the sides act similarly to a reamer; the bit cleans up the wall of the hole as it drills, for a perfect finish – square, straight and smooth. Compared to a regular twist drill bit, an annular cutter is also more efficient. On a regular bit, you are trying to remove metal across the full width of the bit. On an annular bit, you are only removing metal across the width of the bit's edge, because of the hollow core.