Looking for harder wearing Drill Bits than hss and titanium? Then these Cobalt Bits are for you. Cobalt is well known for its resistance to heat and this is key to its hard wearing properties. Unlike other Cobalt Bits sold on eBay these are Solid 5% Cobalt and can be re-sharpened again and again. So if you are working with hard tough metals then look no further.BlueSpot 13PCE Cobalt Drills (1.5 - 6.5mm) are manufactured from high-speed steel with 5% cobalt for the highest durability. The set features a ground flute for increased accuracy when drilling. Suitable for drilling in iron, non-ferrous metals, plastic, steel, stainless steel and wood. Includes useful case for quick and convenient storage. Sizes (mm): 1.5, 2, 2.5, 3, 3.2, 3.5, 4, 4.5, 4.8, 5, 5.5, 6, 6.5.