Check the listing for details. 4 Point Square Socket 1/2" Drive 21mm Metric Socket 1.8" Long 40CR Steel. Condition: New. Listed at 21.47 USD. The specifications of the square socket are engraved on the surface and are clearly visible. You can quickly switch between different socket sizes while working to improve work efficiency.This four-corner drive socket is made of robust 40CR steel, featuring high hardness, good toughness, and strong wear resistance. The surface is forged and phosphated to effectively prevent rust and corrosion, thereby extending the tool's lifespan. The thickened socket wall design allows it to withstand high torque even when using high-pressure impact tools without wear.The impact socket features a square-shaped interface that better fits the square head of the screw or nut, providing a stronger grip, preventing fastener wear, and reducing slippage.