Feature: Premium Quality Made of industry grade 4241 high-speed steel, they own great hardness and strong drilling power. Combo Set of 99 PCS This set includes 13 different sizes of drill bits --- 1.5mm, 2mm, 2.5mm, 3mm, 3.2mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6.5mm, 8mm, 10mm. A great choice for DIY, home and general building and engineering using. Titanium Coated Prevent rust, increase hardness and reduce heat buildup for longer life expectancy. Efficient Drilling Performance Spiral groove design makes smoother chip removal and reduces friction and heat accumulation for higher efficiency. Wide Compatibility You can use it on wood, plastic, copper, aluminium alloy, stainless steel, etc. Specification: Material: High-Speed Steel Total quantity: 99Pcs Sizes: 1.5mm, 2mm, 2.5mm, 3mm, 3.2mm, 3.5nn, 4mm, 4.5mm, 5mm, 5.5mm, 6.5mm, 8mm, 10mm Quantity&Size: 16* 1.5mm, 16* 2mm, 15* 2.5mm, 10* 3mm, 10* 3.2mm, 8* 3.5mm, 8* 4mm, 3* 4.5mm, 3* 5mm, 4* 5.5mm, 2* 6.5mm, 2* 8mm, 2* 10mm Packing list: 99* Drilling bits