Spiral: high hardness, making clean and accurate holes ,multipurpose drilling bit Firewood hand drill cone: made of alloy material, this glass drill bit has very good abrasion resistance and high hardness for longer life,step drill bit Glass drill bit: adopts production to stable characteristics and high reliability,stepped drill bit 4-blade drill: suitable for ceramics, tiles, wood, plastic, concrete wall to drilling hole,auger drill bit, Manufacturer: Akfldms