29 pc Black and Gold Metal Index Drill Bit Set, 1 16 in to 1 2 in Cut dia ORS NASCO Design allows air to flow Design allows air to flow through the slotted hub and between the spirals on the face of the pad visible deformation provides evidence of proper closure Deburred edges reduce risk of damage to parts being clamped Provides a degree of elasticity to accommodate changes in size of the parts being joined helps prevent bit from rusting Turbomax tip starts up to 10x faster Flatted shanks above 11 64" eliminates slippage in drill chuck Reduced shank above 3 8" allows the use of larger drill bits in a 3 8" chuck Rubber overmolded case protects kit if dropped Oxide treatment resists corrosion