High Quality: Compared with ordinary drill bits, our drill bits are treated with titanium plating, which is harder and more durable. Each cutter is made from heat-treated steel for long-lasting, repeatable performance with easily replaceable HSS (High Speed Steel) bits. Excellent design: 4-piece set includes bit set for drilling holes pilot holes for screw sizes #6, #10, #13, #16. Uniquely designed steel countersink pilot hole to allow proper size socket to be installed on screw head, secured with hex key for easy replacement and adjustment. Quick change: depth of adjustable counter sleeve, 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 home and general building/engineering use. At the same time, Christmas gift for dad/father, husband, boyfriend, man, handyman.