DIFFERENT SIZES:4pcs HSS constructed drill bits for drilling holes with screw sizes #6, #8, #10 and #12. SPECIAL DESIG: Special designed steel counter sleeve countersinks or counter bores hole. Drill and countersink for wood screws without changing bits. ACCURACY: These impact bits feature engineered no-skate tips for more accurate starts. PROTECTED: With titanium coating shield, The drill bit set offers less friction than standard impact bits. MULTIPLE USES:Suitable for drilling machines with interface, adjustable for workpieces with hardness below 25HRC, such as carbon steel, plastic, PVC board, wood board, etc.