High Quality: Compared with ordinary drill bits, our drill bits are treated with titanium plating, which is harder and more durable. Each countersink is made of heat-treated steel for long-lasting and repeatable performance with easily replaceable HSS (High Speed Steel) drill bits. Excellent Design: The 4-piece set includes a bit set for drilling pilot holes for screws in sizes #6, #10, #13, #16. Uniquely designed steel countersink pilot hole to allow a suitable size socket to be installed on the screw head, secured with a hex wrench for easy replacement and adjustment. Quick Change: Adjustable countersink depth, drilling and countersinking for wood screws without changing drill bits. The drilling length can be adjusted for different screw lengths simply by loosening and tightening the grub screw. Widely Used: Perfect for plastic, wood and metal, perfect for home DIY and general building/engineering use. At the same time, Christmas gift for dad/father, husband, boyfriend, man, handyman.