ZDD Excellent Material: The drill bit part is made of high-speed steel 4241, which has higher hardness and good cutting ability, can realize fast drilling and offer long term use. The black handle part is made of carbon steel, which can withstand high working pressure and wont brake easily. Accurate Punching: It can quickly and accurately drill a hole. And the outward thread design can help discharge waste chips when drilling, so it can ensure the drilling successfully. Five Different Sizes: Included five sizes of countersinks screw: 5 5/64 /2mm , 6 3/32 / 2.4mm, 8 7/64 / 2.8mm, 10 1/8 / 3.2mm , 12 9/64 /3.6mm Product Feature: The drill bit part is made of high-speed steel 4241, which has higher hardness and good cutting ability, can realize fast drilling and offer long term use. The black handle part is made of carbon steel, which can withstand high working pressure and wont brake easily. It can center well and not skid so that can realize quickly and accurately drill a hole. And the outward thread design can help discharge waste chips when drilling, so it can ensure the drilling successfully. Included five sizes of countersinks screw: 5 5/64, 6 3/32, 8 7/64, 10 1/8, 12 9/64 It is suitable for drilling machines with chucks or joints. It can be used to drill holes on hard wood and plastic boards Specifications: Material:HSS 4241 Number of item: 5 Hex Shank Size: 1/4 Color: Black