Metric length, the best general purpose length for professionals and DIYers. General and Specialized Purpose, for tough materials that normal HSS bits cannot work. Cobalt bits make for some of the cleanest holes and the most durable drill bits, the surest bits for long-life and extended working hours on toughest materials. Straight Shank will fit in any common drill. 1.0/1.5/2.0/2.5/3.0/3.5/4.0/4.5/5.0/5.5/6.0/6.5/7.0/7.5/8.0/8.5/9.0/9.5/10.0mm, a total of 19 drill bits. 1.0/1.5/2.0/2.5/3.0/3.5/4.0/4.5/5.0/5.5/6.0/6.5/7.0/7.5/8.0/8.5/9.0/9.5/10.0/10.5/11.0/11.5/12.0/12.5/13.0mm, a total of 25 drill bits. Twist drill bits are the standard type of bit for modern building construction and are built to be used on, but not limited to, most home fixtures and furnishings. DRILLFORCE provides the ideal twist drill bit with the following features. Cobalt is the longest lasting material when it comes to common drill bit materials, not only will the bit’s structural integrity withstand tremendous heat and wear, but more importantly Cobalt bits can drill through tougher materials than common HSS bits. Made of High Speed Steel containing cobalt (HSS M42), the cobalt giving an auburn color to the metal, is stronger than other HSS bits, meaning that it not only lasts longer but also can work hardened metals and things with denser or tougher attributes that most other bits, no matter the quality, cannot cut. Thus Cobalt Bits are the ideal choise for professionals or DIYers that are looking to take their craftsmanship to the next level with extended working hours and a far more diverse range of materials. With a 135 degree split-point, these drill bits will catch on the work-surface with greater ease and not wander all over the surface making scratch-marks. This means that after securing the bit in the machine all that is needed is a steady hand to point and apply pressure, and that’s it. The straight shank of our bits means you can use this drill bit with nearly all types of machines. The Metric length is the most commonly used length to diameter standard of drill bit, the length is scaled according to the diameter of the drill head to give maximum force with maximum support so as to keep the bit from bending under the pressure, all the while keeping the machine a comfortable distance from the surface so as not to come in contact and scratch it.