3/8" Drive x 3/8" Universal Joint Made with a locking pin retainer Tested to the highest specifications to deliver outstanding performance at the most competitive cost Made of high quality steel (chrome-molybdenum)Lifetime Warranty This 3/8" drive 3/8" universal joint has a locking pin retainer, which is a socket retention device. A spring loaded pin, simply line up with socket retainer hole and press pin. To release socket, insert object through the retainer hole and press pin.