General and Specialized Purpose, for tough materials that normal HSS bits cannot work. Includes 25 pieces each of 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.