All LTT Screwdriver bits are made from S2 tool steel with a black phosphate coating. This type of steel provides a great balance of strength and rigidity - it's strong enough to hold up to daily use in casual and professional settings, and resilient enough to keep up with our ratcheting driver. The black phosphate coating provides a nice industrial look and improved rust resistance over standard S2 steel. At 20mm these bits are perfectly sized to fit in the bit clip within the handle of the LTT screwdriver, so whether you're screwing Phillips and Hex all day on the jobsite or disassembling electronics in the shop, you should have whatever you need right at your side.NOTE: Bits are a consumable item and will wear or break down over time. Visual wear to the black phosphate coating is normal and expected.