Premium Material - The extension bit holder is made of high-quality steel, and the sleeve is made of high-quality aluminum alloy, which can achieve maximum durability. Anti-rust, corrosion-resistant and oxidation-resistant. 5 sizes of drill bit extension - 50mm, 60mm, 100mm, 150mm, 300mm, to meet your different needs, perfect for reaching tight corners and confined spaces. Built-in Magnet - The bottom of the hole is equipped with a permanent magnet that can hold the bits in place, ensuring that the bits stay in place and do not wobble during use. Improving Work Efficiency - The bit extender is very useful for removing or tightening a large number of screws after starting or loosening them. Ideal for working with hard-to-reach screws. Universal Size - Compatible with power drills, screwdrivers, impact drivers, and various other tools, these extension bit holders expand the functionality of your equipment with their 1/4-inch hex shank.