COMOWARE Cobalt Drill Bit Set, 115Pcs M35 High Speed Steel Twist Jobber Length for Hardened Metal, Stainless Steel, Cast Iron and Wood Plastic, 1/16″-1/2″, with Metal Indexed Storage Case. [115Pcs Drill Bits Size] 29pcs Fractional Size:1/16 to 1/2 in 1/64th increments; 26pcs Letter Size: A To Z; 60pcs Numbered Size: #1 To #60. [Enhanced M35 Steel] Drill bits are made from M35 steel (industry grade HSS with 5% cobalt), harder than 4241 HSS used in other similar drill bits, making drill bits more durable and higher heat & abrasion resistance. [Self-centering Design] The 135 degree split point design delivers great self-centering performance and reduces bits walking. The fully ground bit construction decreases friction during drilling, easily for drilling materials includes stainless steel, cast iron, alloy, wood and hard plastics. [Professional & Wide Use] M35 Cobalt HSS is more suitable for hardened material. Particularly successful in cutting through hard metals such as stainless steel, cast iron, high temperature alloy, titanium alloy, hard plastics and woods, and also can be used for softer materials. [Organized Holder] Set includes the drill bit holder with size index for easy storage and organizing.