These corrosion-resistant screws have large, flat sides that prevent sockets from slipping. Since they have four contact points, they also give you reliable torque but slightly less than external hex drives. Made of stainless steel, they won't rust, but they're not as strong as alloy steel. The tip has thin edges that dig into surfaces for a secure hold. These screws often lock gears, pulleys, and other transmission components onto shafts.