Threaded end fits the CV-3/8 check valve, 230106 filter facet fuel pumps and air valves. Barbed end 1/4 or 3/8 may be used with the fuel line tubing either F4040A or BAI. Use 4-6FJX with F4040A- 1/4 or BAI-1/4. Use 6-6FJX with F4040A- 3/8.