PTI T15 x 70mm Screwdriver Bit 1/4" Hex Screwdriver bits are typically made up of a shaft and a tip. A screwdriver bit's shaft is typically hexagonal in shape, with six flat sides. This shaft is fitted into the end of a screwdriver that has a bit holder. The shaft's shape prevents the bit from rotating within the bit holder. The tip end of a screwdriver bit may have many shapes.The bit's head is designed to fit into the head of a screw. As the screwdriver is spun, the bit rotates as well. This is what causes the screw to turn. Head style: Torx Length: 70mm Torx bits are shaped like 6-sided stars, and are utilised on everything from consumer electronics to cars. They are more resistant to cam-out than Phillips or slotted bits, as they allow a more even distribution of force.