Super premium, muti-diameter 3 piece step drill bit set (3 flats). 1/8-1/2, 3/16-7/8 & 3/16-1/2. Made in the U.S.A. Special moly alloy steel. Gold surface treated for maximum lubricity. Dual flute construction, drills clean accurate holes in thin materials, quickly and easily. Use for all thin metals, rigid plastics such as plexiglas and wood or composite materials with a thickness equal to or less that the step thickness. When drilling steel with 1/8"" or greater thickness, a starter hole of the smallest step diameter will speed the drilling process.