Features: Material: Made of premium carbon steel quality makes the drill bits set more durable and wear resistant. Size: There are 7 different sizes to use, 3, 4, 6, 8 10 and 12mm, which can meet your daily working needs. Applications: Ideal for drilling ceramic tiles, glass, marble, wood, brick wall and mirrors. When drilling hard materials, please use water for lubrication to extend the service life of the drill bit. Easy to Use: These drill bits are typically used with electric drills, easy to use and store. 1/4 Shank: The drill bits with 1/4 inch shank are used widely.