The high-speed tapered drill bits are precisely ground on a CNC grinder and match the shapes of wood screws so that screw threads grip for the entire length of the screw. The drills are multi-purpose and will serve the needs of most woodworkers for both hard and soft woods. 2 3/4" to 4" long overall. For softwood, you should always use a drill one size smaller than the screw calls for. Also available as complete drill bit/countersink/counterbore units for a specific screw size – the unit includes a countersink/counterbore, drill, stop collar, and a hex key - or in boxed sets with countersinks/counterbores, stop collars and hex keys.