The fuel pump is held in to the tank with a retaining lock ring. Most people would take an extension or punch and tap out the ring with a hammer. But that's the wrong way to do it. You could damage the lock ring, or worse, the tank itself. This handy tool is toothed to match the lock ring and takes a standard 1/2?drive ratchet or small extension. Twist the ratchet and the lock ring comes un-done cleanly and smoothly. A hefty tool that pays for itself over and over. Fits most BMWs from 1988-2013. Also has application for MINI and Porsche.