【S2 Alloy Steel Hex Bits】 All the facoow hex bits wre made of premium S2 slloy steels, which makes the tips harder and tougher. All the allen wrench drill bits were CNC machined, achieved negative tolerance: 0.2mm less than international standard. All our Allen key bits are precise fit, which is essential for optimal performance while working as a machine or automotive repaire kits. 【21pcs Security Bits & Bit Holder】The 21pcs hex bits set includes Metric hex bits (1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 5mm, 6mm, 7mm, 8mm) and SAE hexagon bits (5/64”,3/32”, 7/64”, 1/8”, 9/64”, 5/32”, 3/16”, 7/32”, 1/4”, 5/16”; 2.3"), also specially put a bit holder inside the box with the drill bits. 【Colored Recognition Allen Wrench Drill Bits】Yellow protective covered Metric bits & SAE red protective covered bits , to make it easier to identify the allen key drill bit set. The color coding cover help to achieve a fast pick-up when you need, making your work more efficient. When the colored protective covers enhance rust resistance, the manganese phosphate finish is also rust-resistant. 【Multi-purpose Allen Key Drill Bits】Full essential size to meet multiple needs on car repair/ home improvement/ bike repair/ ebike repair/ machine repair/wood working. Also got a storage little box for the bits, makes the set more convenient to be organized and carried with users. A muts have hex bits set to supplement your home or work repair kit. 【Facoow Assurance】We are a comprehensive supplier that sales our own integrating product design, production. We not only strived to provide superior products, but also take every effort to offer excellent service.To make work happier and easier is our main gaol. If you have any questions or problem of our item, please contact us directly via email and we will provide you with the best solution as soon as possible.