4 Piece, Speedbor, Countersink Wood Drill Bit Set, Tapered Drill With Widened Flutes For Drilling Fast, Clean Pilot Holes & Ensures Tight Fit For Screws, Adjustable 4 Cutter Counter Bore Cuts & Clears Chips Quicker For Fast, Smooth Countersinking, Counter Bore Attaches To Flats On Shank With 2 Hex Screws For Secure Fit & Can Be Adjusted For Controlled Pilot Hole Depth, 1/4" Quick Change Shank Reduces Slipping In Standard Chucks & Is Compatible With All 1/4" Quick Change Chucks, Including Impact Drills, Adjustable Stop Collar Attaches To Counter Bore, Set Includes: #6, #8, #10 & Small Depth Spot.