This high-quality valve solves the problem of fuel management for vechicle and  vessels equipped with fuel injected and diesel engines. Supply and return lines are switched simultaneously and the fuel is returned to the same tank it came from, avoiding fuel spills and complicated multiple valve arrangements. The valve has 4 selector positions: L/R/Both and OFF with very definite "Click" detent when centered on the port. Very smooth operation. The stainless steel ball and the valve ports are isolated with low friction seals. No metal to metal contact. 20,000 leak free cycles.