Professional contractors rely on DEWALT Self-Feed Wood-Drilling when they need to bore extra-large diameter holes for pipes, cables, and ductwork. These ultra-heavy-duty bits feature a double-cutter design that reduces binding and stalling, and a self-feeding screw-tip point that helps pull the bit through the material. And because there are flat surfaces machined into the shank, there?s less chance of the bit slipping in the chuck. Includes 5-1/2-inch extension, 1-, 1-1/8-, 1-1/4-, 1-1/2-, 1-3/4, 2-1/8-, and 2-9/16-inch self-feed bits.