Whiteside 4 Pc. Tapered Drill Bit & Countersink Set is expertly designed to bore a countersink for flat head screws while simultaneously drilling a hole that perfectly matches the screw size and length. This set features 4-flute, 82 carbon steel countersink heads that slip over the drill bits and are securely held in place with dual set screws that fit into the flutes. Adjusting the drilling length is simple by sliding the head up or down the bit. The matching drill bits have a tapered point to resist rapid pull-in tendencies, especially in gel-coat and other hard, thin materials, reducing abrupt break-through and minimizing blowout on exit. These versatile bits are suitable for use in wood, plastic, or aluminum. The set includes four sizes designed for #6, #8, #10, and #14 screws, all housed in a convenient plastic storage case. Manufactured by Whiteside Machine Company in Claremont, North Carolina.Model Number: 8067774