145 Pieces Set Includes: 29pcs Fractional Size: 1/16 to 1/2 inch bits in 1/64th increments; 26pcs Letter Size: A To Z; 60pcs Numbered Size: #1 To #60; Set includes the drill bit holder with size index for easy storage and organizing Perfect Drill Bits: Precision grinding process for a clean surface and high grinding accuracy. Universal round drill shank, widely applicable to tool holding systems and tightly clamped 135° Split Point & Twist Design: The 135-degree fast cutting point is automatically centered and penetrates quickly with less pressure, reducing walking, fully ground drill bit with a sharp and durable cutting edge. Twist design for clear chips faster Enhanced M35 Alloy Material: These drill bits contain 5% Cobalt alloy steel, which increases wear resistance and durability. Industry grade M35 high-speed steel drill bit set, harder than 4241 HSS used in other similar drill bits set Professional After-Sales Service: The outer box for the stepped drill bit is sturdy and easier to carry and store.