1、Perfect for wood, fiberboard, particle board, plywood, plastic, PVC and soft metal. It is suitable for hand drill, bench drill and electric drill, but not for cemented carbide or steel plates. 2、Three pointed design, quickly and accurately drill a smooth hole, without offset, slip and bias, better in centering and no skid . 3、These countersink drill bits are made of industrial grade high speed steel, which provides hardness, superior cutting power and durability. 4、Easy to use the combination of wrench to adjust or disassemble the countersink drill bit and the chamfering. 5、High working efficiency, with 3mm, 4mm, 5mm, 6mm, 7mm, 8mm,10mm model, the drill bit set is very suitable for household and DIY Projects.