539-08-206 Fuel Line Ferrule Sleeve , fits 356A and 356B with early fuel pump

539-08-206 Fuel Line Sleeve , fits 356A and 356B with "early" fuel pump. 

For 356A thru 356B engines with “early” fuel pump – The ferrule, sometimes called a sleeve, goes over the fuel line after the compression nut.  It forms a seal when the compression nut is tightened against the union fitting.  Since this ferrule is distorted to form a seal, it’s best to replace it whenever the pump is serviced.