Premium Material: 6542 HSS Carbide with a reinforced head that prevents bit cracking; Twist drill bit set made of hard and durable alloy, provides longer life. Unique Design: U type slot design with fast drilling dust remove, antiskid triangle handle allows the drill bit to be held tightly and stable in a power drill. Wide Usage: Spear pointed design strong tungsten carbide tip can easily penetrate various materials like tile, concrete, brick, glass, plastic, and wood, etc, and reduces breakout. Drill Bit Set with 4 Different Sizes: 6mm(1/4"), 8mm(5/16"), 10mm(3/8"), 12mm(1/2"). Tip: When drilling hard material such as glass, porcelain floor tile, marble, granite, etc, please use water for lubrication. Color:Red,Orange,Gold,Blue Size:5Pcs/Set(6mm,6mm,8mm,10mm,12mm) 7Pcs/Set(3mm,4mm,5mm,6mm,8mm,10mm,12mm)