The 1/2" DRIVE 1/2"F X 3/8"M Adapter with FOUR FLAT Sides is designed from the ground up to be part of the most versatile socket family. Milwaukee adapters feature an innovative design with four parallel flat sides, which deter rolling and are wrench-compatible. The drive sizes are laser etched onto the adapter providing improved, easy-to-read visibility. Chrome plating offers corrosion and rust protection. All Milwaukee Mechanics Hand Tools are backed by a lifetime guarantee.