The 3/8″ Drive Metric Hex Sockets with FOUR FLAT are designed from the ground up to be the most versatile socket family. MILWAUKEE sockets feature an innovative design with four parallel flat faces that reduce the risk of rolling and are ready for use with an open-end wrench. Socket sizes are stamped on the flat faces to provide improved readability. These standard and deep sockets feature optimized geometry to reduce rounding and tearing of bolt heads. All of the sockets are backed by a lifetime warranty.