This is the best grade of HSS steel. True engineering quality. This drill pieces have been fully precision ground and heat treated for extra strength and durability. Fully ground bits are machined from a single bar and are better that a normal rolled or drill bit. They are also more expensive to manufacture. These have a long lasting working capacity and use an aggressive 135 Degree Split Point Design. This set also comes with l carry case so you can keep organised in their and tidy positions. Starting at 1mm these drills increase in size in 0.1mm increments Hss 135 Split Point Color: Silver Ground high speed steel (HSS) General use for wood, metal and plastics Sizes from 1mm to 6mm in 0.1mm increments Package Contents: 51 x drill bit set 1 x Box (Color Random, can not color) Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.